Which DC superhero is coming out of the closet? Yawn. Such original storytelling.
Dumbledore!
If profits are still important to DC and it’s a major character coming out, then of course it will be Wonder Woman. Sales losses will be minimal, and they might see a sales boost, at least short-term.
Also…speaking as a storytelling geek, there are serious issues to consider. A hero who suddenly comes out as gay had better not have a serious hetero-romantic relationship going on. “Lois, I know we’ve been flirting/dating/married for decades now, but I, Kal El…am actually hot for the dudes.” And the Diana Prince/Steve Traynor Trevor thing has been trivial for generations now.
(Diana Prince is Wonder Woman’s non-Amazonian name, for you non-geeks.)
I’d laugh if they made Batman gay, but they wouldn’t dare. First, because he’s the Gee Dee Batman. But “I piss on childhood memories” artistes don’t care about that. No, it’s because Bruce Wayne has adopted, like, three 13 year-old boys over the years. Heh heh. Yeah, that’d really advance the gay cause.
As for the other major DC heroes…
…
…there aren’t any.
Hey! Assuming Superman isn’t gay, doesn’t that mean Bizarro has always been?! God, there’s a scary thought.
World's Only Rational Man 
Who cares? Batman, for example, is about going vigilante on the bad guys. His sexual orientation is irrelevant.
…so it’s turned out to be Alan Scott, the original Green Lantern from the 1940s.
Ace has the details.
Attaboy, DC! Nothing like standing up for gay rights, I always sez!
*rolleyes*
“This is on the level of revealing that Mr. Mxypltzyk is bi.” Good ol’ Ace! Thanks for the update.