I doubt they will add peoples favorite obscure chars.
I would say yes, she's currently in the spotlight at Marvel Comics, so if she's in an ongoing comic there is a high chance we'll see her in MPQ, current characters is what Marvel wants to promote.
Warlock, while being my favorite Marvel character has not been in a recent comic, other than Jim Starlin's recent graphic novels that is; I don't see them adding Adam Warlock/Magus to the game anytime soon, if at all.
Dr Strange is very likely to be one of the new characters to launch before the end of this year, he's part of the current ANAD lineup at Marvel.
Gambit am not too sure of, I don't really follow X-Men comics.