Capcom-Unity blog, producer Derek Neal revealed that development on the PC version of the SSFIV Arcade Edition Ver. 2012 update is currently coming to a close. Capcom hopes to have the update out on February 28, though nothing is set in stone.
The Arcade Edition Ver. 2012 update has been available on consoles since December, and implements balance tweaks across a multitude of characters. The changes have been well documented, so study up if you're looking for immortality in the streets.