TSSZ cite an anonymous source that notes the existence of a Vita version of Sonic Generations. The website predicts that the game will launch alongside the PlayStation Vita's launch in Japan this year and the West next year.
The website also predicts that SEGA may be developing Yakuza 5 for Sony's new handheld. No details were given other than the word of its source, but we know the game exists after its announcement on September 1st.
If the Sonic Generations rumour is to be believed — and we'd put money on it — expect an announcement to be made this week during TGS.