Gorilla Gunk said:
Come one, we all know it's going to be Aquaman.
No, there's pretty much no chance that it's Aquaman. The currentNew 52 Aquaman story (which is written by DC legend Geoff Johns and is actually one of the best of the New 52 series) focuses really heavily on the relationship between Aquaman and his wife Mera. To announce that he was suddenly gay would upset the most developed relationship in the current DC universe.
The same goes for The Flash, whose comics have played on the "who will he choose in the end" drama between love interests Patty Spivot and Iris West, who are both women. And considering that the latest Green Arrow story arc was built around Oliver Queen (whose last name would have made him WAY too ironic a choice in the first place) getting seduced by identical female triplets, the best they could hope to realistically hope to convince anyone of was that he was bisexual. This also goes for Batman, who not only has a long history with so many women it's amazing he hasn't contracted Bat STDs, but also has a son, and has been with a number of women even just in the New 52 story-lines.
Next is Martian Manhunter who seems improbable for a number of reasons. Forgetting those related to cannon however, as they do remain in Martian Manhunter's case in a state of potential flux since the New 52, the logic of making the current Martian Manhunter gay as a publicity stunt would make no sense. First off, he's lost some of his iconic status as he's no longer a part of the Justice League, and instead is a part of Stormwatch. Secondly, Stormwatch already has the DCU's two well known gay characters, Apollo and Midnighter, so the choice to add a third to the team would be pretty ineffectual in terms of how much it would shake up readership. Not only that, but seeing as MM is the last martian, even if they made him gay there'd really be no where to explore that storyline without resorting to flashbacks.
The first Green Lantern (Hal Jordan) also seems improbable for the same reasons as Aquaman and Flash, specifically that his on again-off again relationship with Carol Ferris has been a recurrent part of the current storyline. The remaining three human lanterns are still possibilities, John Stewart, Guy Gardner, and Kyle Rayner, but none of them seem quite iconic enough.
It seems improbable that any of the Robins are gay (all of them but Damien [who is a little young] have at the very least implied interest in a girl within the context of the New 52 story-line). Nightwing might have the profile, but they've played with his relationships both with people from Haley's circus, and with Barbara Gordon (Batgirl). Tim, who's serving as Robin for the Teen Titans seems to have a thing for Wonder Girl, although the presence of Bunker on the team, who has already been established as gay, would play easily into the drama if he were the one. And Jason Todd (AKA The Red Hood) had slept with Starfire before Red Hood and the Outlaws even kicked off, though she's with Arsenal now, so I guess he's free.
The safest bet is probably Cyborg. His past as one of the main characters in the long running Teen Titans show, and his current status as a member of the Justice League certainly give him the high profile status. There have been no implications about his sexuality one way or the other within the New 52 DCU, and it would certainly bring a new angle to the strained relationship he has with his father.
The other possibility though, which I actually find far more interesting, and which could pay some big dividends for DC if they were ballsy enough to do it, is Superman. Supes has been long past due for a love interest who wasn't Lois Lane, and the current storyline would definitely be set up to handle such an announcement. New 52 Lois has been dating around quite a bit, and while there has been some implication that Clark might be interested in her, it really hasn't been anything more than just that... implication. He's also rejected attempts by other women to be with him, and his current moodiness in the comics would be very interestingly explained by the realization that he's been mulling over whether or not to come out of the closet.
And the politics of such a change couldn't be better timed either. Unlike Batman who has a fanatical following amongst the comic book reading populace, Superman has a very low readership. That is to say that he lacks appeal to the fan base he's currently trying to attract, and a loss to the already minuscule readership would not be devastating. Making Superman gay could revitalize the character in a big way if handled right. The current perception of Superman as symbol of "good old fashioned American values" (IE the perception of Superman which has lead to his wild unpopularity) would by necessity go right out the window as he embraced new liberal values. And the use of one of DC's two most iconic characters in that role could potentially attract the interest of a number of non-comic reading demographics as it would serve as an undeniable symbol of political view and good will on DC's part to make such a big and controversial change. There might perhaps even be some comparable precedent in a storyline occurring before the events of Flashpoint in which Superman renounced his American citizenship, another attempt by DC to reach out to those of a more liberal leaning and reject the Superman as boy-scout perception. That is to say that DC has been looking for something big to shake up and revitalize Superman for quite a while, and this would definitely qualify.
So while my money's on Cyborg, I'm going to go on hoping that it'll be Superman. I guess I'll just have to wait and see though.