Because every Internet leak is true (confirmed!), it’s been made official that Akuma and Marvel’s mimic Taskmaster will appear in Marvel vs. Capcom 3.
IGN has the reveals, along with some videos, which show the two in action. Both characters will be unlockable; Eurogamer reports that Akuma will appear when you earn 2000 PP, and Taskmaster at 8000 PP. PP is Marvel vs. Capcom 3’s experience-like system, with a single arcade playthrough apparently netting you 2000 PP.
If the mostly-spot-on rumors are to be believed, Capcom has a few more characters up its sleeves, including Darkstalker’s Hsien-Ko, Sentinel, and Galactus. Marvel vs. Capcom 3 is out in just a few weeks, so it won’t be long until all is revealed.