You only need look to this month, when it is scheduled to release Ultimate Marvel vs Capcom 3. The non-Ultimate version released earlier this year.
But chatting with Gematsu, Capcom fighting guru Yoshinori Ono has told the website not to expect any boxed versions of future Street Fighter X Tekken updates: "I would say that you don't really need to worry about a new version of the game coming out. If we choose to update the game, it will be done in the same fashion as Super Street Fighter IV: Arcade Edition." (Arcade Edition was released as a DLC pack for existing owners of the game.)
Ono added that Street Fighter X Tekken will run on new netcode, though the advantages of which weren't explained. Obviously eliminating lag is a big deal for fighting games, and while recent Street Fighter releases have been pretty good at this, there's always room for improvement.