Marvel vs. Capcom 3 isn't even out of the door yet, but Capcom has already decided to start the promotion drive for the first batch of downloadable content that we'll see in the game. It's been dubbed Shadow Mode, and will be put out in a series of different packs.
Each pack will allow you to fight against "custom-built computer opponents, modelled after famous players and specific themed teams." In other words, it'll be like dream matches against AI.
The first team will be based around the game's producer, Ryota Niitsuma, while Akiihito Kadowaki will also have a team.
There has been no price confirmed for any of the packs, but Capcom did reveal that the DLC would be made available at some point during March. The game itself launches on the 18th of February in Europe.
Source: Capcom Unity