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The trailer mentions 35 characters, which would be the characters from the console releases of Super Street Fighter IV, but not the arcade version's Yun and Yang.
Two additional features are also introduced. The first, Figure Collecting, will automatically battle other players that walk by using the 3DS tag mode feature. When passing another player, your collection of figures, seemingly based upon playable characters, will battle theirs. Winners will earn more figures.
The second feature is Arcade Standby, which looks to facilitate wireless multiplayer matches between nearby players. This seems to be similar to the way the Fight Request system functions on the home versions of the game.
The Nintendo 3DS will be released in Japan on February 26, 2011 and should hit the US and Europe by the end of March.