If this turns out to be true, it probably has to do with Ubisoft's annual release business model for their major franchises. To be honest, I don't blame him... I guess we'll find out at E3 if / when Ubisoft unveils AC: Brotherhood and, if he is still on board, chances are he'll be doing the unveiling.
"Ubisoft responded to our story with the following statement: "With his role on project essentially done, Patrice Désilets has decided to take a creative break from the industry and is no longer working on Assassin's Creed Brotherhood.""
Lulz, wtf is a 'creative break'? Is he taking some time off to compose a symphony or something?