They were able to do it although they were only able to put Marvel (I don't think they'll be able to include both Marvel and DC in a single videogame). All the Marvel expansions are in the game except the new X-men and the upcoming Heralds of Galactus sets. I don't know about card balance; some meta cards are gone without DC. Seems to be a combat-oriented environment except for Doom and X-men Stall. Still, this might be cheaper than getting a set of those rare Dr. Doom singles.
Images:
http://www.pulparcade.com/2006/05/11/images-galore-of-the-marvel-trading-card-game Trailer:
http://media.ds.ign.com/media/827/827065/vids_1.html ---
In other news, I want to watch MI3 because if its director, but everytime I see Tom Cruise on the poster I change my mind.