Looks as if those leaks were true. Capcom officially announced Marvel Vs. Capcom 3 this morning, due out in 2011 for the PlayStation 3 and Xbox 360. Check out the trailer and a bit of official art here.
It's uncertain at this point if any Mega Man characters will take part in the game, but considering Mega Man, Roll, Tron Bonne (and Servbot) were playable in the first two installments, I'd say it's likely someone will show up this time around. I'll keep you posted.
Thanks to everyone who sent this in!