CapCom Unity has details on the third beta session for Street Fighter IV, saying this will begin tomorrow for Windows and PS4. They outline the characters and game modes this will include, and offer a detailed schedule of tests. A separate post outlines plans for Steam OS support in the brawler sequel, and how the test will include Steam Controller support:

Hey everyone. I’m excited to announce that Street Fighter V will be officially supporting Steam OS! We are working closely with Valve on this endeavor, and will have more details to announce in the near future, so stay tuned for updates.

Street Fighter V will also support the Steam controller, and you’ll be able to try that out right away during the upcoming beta test that takes place from December 18~20.