Sega's VP of marketing and sales, Alan Pritchard had more to reveal in his recent interview with Game Informer. He mentioned: "We have a further title to announce from Platinum Games."
Sega have released four titles developed (Mad World, Bayonetta, Vanquish) or produced (Infinite Space) by Platinum Games, thus fulfilling the original agreement between the two companies. But now there is seemingly a fifth title on the way. Given that Bayonetta saw both good reviews and reasonable sales (especially in Japan) there is a good chance that a sequel is what Sega and Platinum Games plan to announce.