Producer Yoshinori Ono, who is scheduled to announce his next game at Comic-Con on July 24, discussed the possibility of patching the home versions with Famitsu (translation by Andriasang), saying "If it's a tuning update similar to the June 15 update, I believe we'd be able to offer it for free. However, if it's the kind of update that adds new moves, it's possible that it could be paid."
This seems to open the up the possibility of development to continue adding characters or moves, but it is unclear if this is actually part of Capcom's plan for the arcade release. Balance changes are planned, but will be addressed after the game is ported to the arcade hardware.
I reached out to Capcom for a clarification, but was told that "Capcom does not comment on speculation or rumors." No release date has been set for the arcade version of Super Street Fighter IV or if it will be released outside of Asia.