From UDON’s blog

Just announced in Famitsu Magazine is the return of three Street Fighter favorites in 2010’s new Super Street Fighter IV game. Last seen in the Street Fighter Alpha game series, players can look forward to the return of:

• Adon – The wild jaguar of May Thai, and Sagat’s former pupil.
• Guy – The 39th master of Bushin-Ryu ninjitsu, and one of the heroes of Final Fight’s Metro City.
• Cody – Another Metro City native, this fallen hero now spends his days in prison, occasionally breaking out to find some street fighting action!

UPDATE! Looking at the Famitsu scans, Shoryuken points to evidence that SF3’s Ibuki will also be in Super Street Fighter IV:

If you take a peek at the top right of the image featuring Guy, you will see Guy punching a kunai (ninja knife) out of the air. To further confirm that it is indeed a kunai, the text next to that image playfully asks who’s kunai Guy is punching.