Capcom's Ryota Niitsuma, producer of Tatsunoko vs. Capcom, has discussed some of the changes in the Western version.
As well as the required language translations and voice-overs, fans can expect a few new character additions (likely to replace those that'll have to be removed), as well as fixes to some of the balancing issues and glitches in the Japanese edition.
VideoGamer.com: Will there be any differences between the western version and the Japanese version?RN: Quite a lot actually. The biggest feature would be the addition of new characters, but we will also be tweaking the design of the interfaces. We will be changing some sounds. We will be re-recording voiceovers, we will be recalibrating game balance given the responses we had from the Japanese users, obviously minor bug fixes, and we will also be changing the content of the mini-games that were in the Japanese version.
For more details, be sure to read the full interview with VideoGamer.com. Thanks to GoNintendo.