Ubisoft revealed in its quarterly financial statement that a new Prince of Persia game was coming in its fiscal year 2008-2009. That would land a new Prince title sometime between April of this year and March of '09.
The financials do not state what platforms will be home to the new Prince of Persia. The team that created the critically acclaimed Prince of Persia: Sands of Time worked on Assassin's Creed. It's unknown which of Ubisoft's development studios is working on the new Prince title.
Ubisoft declined to expand on the sleight-of-hand Prince of Persia announcement.