Ultra Street Fighter 4, which must be the last revision since Capcom is running out of superlatives, has moved out of its previously nebulous "sometime in the future" release window. Capcom has announced that it will release next year, sometime between April and July.
A post on the Capcom-Unity blog states that it will hit arcades in Japan in April, with the downloadable version hitting North America "soon after." It specifically notes that will happen before Evo, which is scheduled to start on July 11, so that gives a nice solid three-month period for it to fall into.
The update will include new fighters, and new options like the Ultra Combo Double and Red Focus Attack. If you already own Super Street Fighter 4 Arcade Edition, you'll be able to grab the update for $14.99. Otherwise, it will be $39.99.