Which super characters could believably play for the other team?
BTW who/what are the current mainstream Marvel and DC gay superheros (if any)?
I hope that by “go gay” you mean come out of the closet as gay, since heterosexuals do not “turn” gay. (Unless they decide to have a really Mature-rated story arc involving mind control 
)
Other than the characters who have explicity been involved with the opposite sex (and even they could be bi), I don’t see why any character could not come out as gay.
DC has:
Pied Piper, a former Flash villain, now an ally.
Maggie Sawyer, a former Metropolis Special Crimes Unit detective, now on the Gotham City police force.
Terry, the assistant of Kyle Rayner (Green Lantern).
Marvel has:
Northstar, an effeminate Canadian mutant and member of Alpha Flight.
WildStorm has:
Apollo and the Midnighter, members of the Authority, who are a loving gay couple. They started out like “swipes” of Superman and Batman, but have evolved into their own characters… neither have any problem with killing, for example, and they do it quite often. The killing, I mean.
Also Marvel has the Rawhide Kid, an adventurer set in the Old West.
It’s a cliche by now, but I’ll have to go with Robin.
Aquaman/Aquaboy
Northstar’s been promoted from Alpha Flight to the X-Men, so he’s more high profile now. He’s a really cool character and I wish he had more screen time, but he has to compete with about fifty other characters on Uncanny X-Men so sometimes he disappears for issues at a time. Dang it.
The Human Torch. He hasn’t been in a believable heterosexual relationship yet and strikes me as a bit of a misogynist (the “chippie” comment in Secret Wars, the manhandling of a female fan in Fantastic Four 1234, the sham marriage to a sham Alicia, etc.). I could see him rediscovering his sensitive side at a Judy Garland retrospective.
Killraven. His best stories were drawn by an outspokenly gay artist, P. Craig Russell, and he dresses in the most fetishistic manner imaginable. Have they ever even claimed he isn’t gay?
Storm. Yeah, they keep putting her in these not-too-believable relationships. The times she smouldered the most were when she hung out with Kitty Pryde. Not a huge stretch.
Nick Fury. The booze, the broads and the really big guns seem a little forced after all these years. What are you running from, Nick?
Conan. Girding his mighty thews all over the place. Take it to the gym, dude!
I’ve fought it as long as I can, but I’m breaking down now.
Batman. If he was prepared.
Sorry about that.
I would love for Robin to come out. Tim Drake is adroable. I’d buy it, too. I mean, he’s been dating Spoiler for how long? And no sex? Uh huh. Gay. Gay gay gay gay gay.
Lobo - to Macho/trying to hard, has to be covering up for his latent homosexuality.
Here’s another gay-comic character database, BTW.
Harley Quinn and Poison Ivy, obviously.
Superboy could easily be “overcompensating.” (Sorry, Batgirl)
And for the “X-Men: Evolution” fandom, I understand that a “cult following” of sorts has arisen to speculate on the sexual orientation of the Brotherhood of Mutants.
That comic book was so incredibly offensive that it came off as a very nasty parody of what a very uptight straight man thinks gay people are all about.
The Rawhide Kid makes Oscar Wilde look butch.
Spiderman. He’s all sensitive and introspective, and doesn’t he take care of his elderly aunt or something?
Not everyone feels that way about it. Scroll down to item number 4 for his review of The Rawhide Kid.
And here’s another nice review of it.
True, some folks didn’t like it. What confused me was the decision to label it “Parental Advisory Explicit Content”. I’ve read the trade paperback of the Rawhide Kid from cover to cover and there’s NO explicit sex in it anywhere. Heck, the words “gay” and/or “homosexual” don’t appear anywhere in it, either. Overall, it was a lighthearted humorous tale.
Robert Smigel’s Ambiguously Gay Duo.
C’mon, someone had to say it…
Another suggestion…Marvel’s Edifice Rex.
Just look at the last image on that page. Take a good, careful, look.
I’ve been suspecting for a while now that Ultimate X-Men is preparing to have Colossus come out of the closet. I mean, there was that time he and Wolverine were having a conversation about “Shouldn’t a teammate share his feelings with another teammate?” that was very suspect, and then there’s the whole bit where he overwhelmed Magneto because “No one messes with Wolverine!” I’m really susptecting something here.
As for the list you provided, Otto, I’m not so sure about some of them. I mean, Destiny and Mistique, to my knowledge, weren’t lovers, they lived in a mother/daughter relationship. I haven’t really read an “real world” X-Men book in a while, so they could have come out, but to my knowledge, that’s a stretch. And who did Black Cat date? Again, to my knowledge, she’s always been a fan of the Spider-Man.
Did you read it? I did. The straight people at my shop who looked through it agreed with me.
That some people could read it and see light hearted where it came off as stereotypical in a nasty way at times, amazes me.