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.
A trailer was also unveiled. Take a look at it below. Assembled media at Capcom's annual "Captivate" event were told that this trailer was using the same models that will be used in the game itself, though obviously it will look more like a traditional fighting game in its presentation.
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.
The art style in MVC3 is described as a "living comic book," with touches throughout that work towards that goal. Shaders (seen in the trailer) will be employed to achieve this goal, along with more integrated use of the Marvel side's catchphrases, comic book-style openings and endings, and so on.
The game's roster hasn't been announced beyond the characters seen in the trailer. In case you're reading from somewhere that doesn't support Flash, that roster currently includes...
Redfield is the only true newcomer on this list, and he's shown in his Resident Evil 5-era attire. The game will contain some form of online play, but the details on modes and so on aren't available at this time.
There really aren't many more hard details out there about the game, but considering it's still a year away, that's to be expected. Speaking of expectations, I'd expect we'll hear more about Marvel vs. Capcom 3 at E3 in June, and perhaps again at San Diego Comic-Con.