The short answer is: it’s complicated.
The slightly longer answer involves the difference between “queer” and “homosexual.”
Actually, you know what? Let’s talk about that. I think it’s worthwhile.
So, briefly: I think that Sherlock and John are a canonical queer couple. I feel that has been demonstrated as unequivocally as it’s possible to do without them actually making out or something.
They have not, thus far (as I think we’ve all noticed), been demonstrated as an unequivocally homosexual couple.
But queer does not necessarily equate to homosexual.
Ceasing to be brief (Jesus, I should install a read-more in this thing): My canonical read on them at this moment—the thing that feels actually true to me, what I see in the show and think that I can reliably argue and support with evidence as outright being there—is that Sherlock and John are in a committed asexual relationship.
Not just a friendship, although it can be hard to explain to people who haven’t had one what the difference can be. An actual committed asexual relationship.
I really love this one, you’ve laid it all out so perfectly, but I do have one thing to add (or suggest, perhaps?) and that’s that even though I think John is the connecting point in the Sherlock/John/Mary relationship I still think Sherlock and Mary has something other than their love for John. Sherlock hasn’t been very pleasant to the ones of John’s girlfriends we have seen (not ever Sarah, even though he sort of, kind of, comes around a bit maybe?) and I think it’s reasonable to assume that he didn’t treat the ones between Sarah and Janette any better. Mary on the other hand…
It could be argued that he does it because he recognises that John needs her and that a huge part in getting John back in his life is to accept her presence there. The same goes for Mary. She’s more positive about Sherlock’s return from the very start because she knows it will make John a more whole and happy person. I think, however, that they, in each other find a person to relate to. Mary is shown to understand some of Sherlock’s actions instinctively (He would have needed a confidant.) and Sherlock doesn’t seem very upset about that she has shot him, but rather that she hasn’t trusted him with her secrets because he could have been a support and a help. I believe that they relate to each other in some ways better than John does with either of them, because they have lived outside the law, taken it in their own hands and done things for the greater good (see: People like Magnussen should be killed. That’s why there are people like me.) and have to live with the consequences of that, both practically (Sherlock’s strained relationship with John, Mary’s non-existing relationship to her family etc.) and I’m sure psychologically.
There might not be a romantic element between Sherlock and Mary, but I don’t think it’s just – and I apologise for the use of that term – a friendship and the acceptance that John needs the other one in his life. I think they are confidants, and in some ways allies, and meet emotional needs for each other that John can’t.
Well, I wasn’t really talking about Sherlock and Mary, because that wasn’t the question. But since you bring it up, I think the two of them have a VERY interesting relationship!
I think you definitely have a point, with them sharing a certain understanding of one another. It’s more complicated than that, though. Mary is cold and ruthless in a way that Sherlock isn’t. Some days he’d quite like to be—and he certainly can be, when he chooses—but I don’t think that, for example, the cool, almost emotionless ability she shows to shoot Sherlock (whom she really does like, I do believe that) is something that even Sherlock can easily marshal.
So I think that furthermore, in Sherlock’s case he may very well feel a certain fascination (and perhaps repulsion) for Mary. I say repulsion not necessarily in a judgmental way, but in a much more personal sense. Sherlock has extremely personal ways of connecting with people. He responds very powerfully to things in them, like Irene and Moriarty and even Janine, he sees as being similar to himself. He responds equally powerfully—as with Moriarty—to things he sees as being similar to himself but that he doesn’t want. This probably even contributes to his utter loathing of CAM, who also exhibits some of Sherlock’s characteristics—intelligence, memory training, skill at manipulating and ferreting out secrets—but uses them for a purpose that is precisely antithetical to everything Sherlock stands for.
I suspect Mary is an example of this for him. We haven’t actually seen it, this is me speculating, but given his past history I am betting he’s got a bit of that going on with her.
He is also, I think, attracted to the ways in which she is like John. I don’t know what she’s like when she’s being AGRA, but as Mary she seems to have chosen compassion, when she can afford it. She knows her neighbors by name. She’s someone they come to for help. For the first two episodes of the season, she’s sweet and good and adorable and stable. That’s who she’s chosen to be for John—who she’s decided she’s willing to be for the rest of her life with John. She’s also bright, unpredictable, a bit weird even when she’s fitting in—all things that Sherlock adores in John.
Mary is an interesting combination of many of the traits we see in Sherlock and John. She’s even a physical combination of them. She bears a lot of physical similarities to John in the same way Irene bore a lot of physical similiarities to Sherlock. But the way she carries herself, watches people, interacts with the world—frequently there’s quite a bit of Sherlock in her body language and attitudes.
And Mary, meanwhile. We have here a woman who has spent her life as a professional killer and, from what she says, later on a criminal. She shamelessly expresses a desire to see CAM dead (not to mention actually trying for it herself). Now that in itself isn’t…well, no, it’s pretty scary in real life, but 1: it may be worth noting that she cares enough about humanity as a whole that she emotionally resonates with the idea that the world would be better off without CAM in it (that is not a ringing endorsement, by the way; it’s more of a minimum standard) and 2: she says it in a room occupied by two men who happen to agree with her. John has pulled the trigger on someone like CAM before. Sherlock is going to do it in a little bit. It’s not the “some people need to die” philosophy that is the problem, for the purposes of this show. It’s the fact that almost certainly, not all the of the people she’s actually killed were monsters.
She warns John that he’ll hate her if he ever knows all that she’s done. She may not care about what the world at large thinks of her (aside from not wanting to go to prison), but she cares very much what John thinks. At least by extension, if not for her own sake, she cares what Sherlock thinks.
But Sherlock is okay with her. Once he starts paying attention, he probably has a better idea of what she’s done than John does. We all know there’s a good chance he lifted the thumb drive and read up on her if John didn’t. And he doesn’t judge, at all. He just takes her as she presents herself. He’s a man who can actually say to himself, “Well, objectively speaking she may well be evil. But I like her personally, and John likes her, and she’s on our side and not inclined to murder anybody I want to keep, so it’s no skin off my nose.”
And especially if Mary actually does want to reform (we don’t know if she does or not, or if she’s made her choices based simply on wanting John), then Sherlock’s effortless acceptance has to mean the world to her. Not to mention, Sherlock may well have the power to take John away from her, but he doesn’t do that.
So. Currently I don’t see anything between them that isn’t platonic. I definitely don’t see that spark of something more that Sherlock and John have burning between them. But the fact that they’re ‘merely’ friends is not to say that there aren’t necessarily some powerful undercurrents running between Sherlock and Mary.
And it says absolutely nothing about however their friendship might develop. They haven’t known each other for long. Less than a year, by the end of the season. They’ve spent quite a bit of time together with the wedding planning—enough for them to feel comfortable and friendly around each other—but whatever potential might exist between them has yet to fully develop.
I am rather looking forward to seeing how that goes in the next season. And I’m quite sure that Mary isn’t done with her secrets cropping up. I highly doubt that we will ever see the intensity between them that exists between Sherlock and John, but I do expect that we’ll see their friendship unfold some more. (And it’ll probably provide something to work with for those inclined toward the shipping.) Unless everything goes to hell and Mary turns out to be a villain or one of her secrets blows up so catastrophically that it disrupts everything. In either of which case, I’m pretty sure that the interplay between Sherlock and Mary will still be interesting to watch.