The game will be running on a version of Capcom's MT Framework engine, which also powered Resident Evil 5 and Lost Planet 2.
This may surprise some folks, as you might expect a new Capcom fighting game to run on the same engine technology that powered its last big fighting game, Street Fighter IV, or perhaps its most-recent versus series game, Tatsunoko vs. Capcom. After talking with a few different Capcom representatives, it sounds like MT Framework is perfectly capable of displaying the fast-moving action that versus series fans would expect.
No one was really too willing to go in-depth on how the fighting system will operate, other than to say that it won't just use the same system from Tatsunoko vs. Capcom (even though that bit at the end of the trailer sure looks familiar). The game will feature over 30 characters and will feature three-on-three tag battles, just like Marvel vs. Capcom 2 did. In case the above trailer doesn't spell it out enough for you, the game will utilize polygonal characters and backgrounds. The game, however, will take place on a 2D plane.