A number of sources tell us that the development team at Ubisoft Montreal that was working on Rainbow Six: Patriots has had the core members leading the project replaced or they were kicked off of the project depending on who you talk to about it.
The decision by Ubisoft to make these changes likely signals that they wish to take the project in another direction rather than continue in the direction that the core of the team had originally charted. Whispers that are going around suggest that the narrative-heavy title didn’t meet the expectations of many who saw it.
The game is scheduled for a 2013 release for the Xbox 360, Playstation 3, and PC, but with this change it is difficult to say if the current production timeline will stay on track.
You can read more about it here.