Welcome to South Park Answers. What would you like to know?

Sometime in 2011 is all we know for sure. Although every season for the last eight years have all started in March, so we can assume season 15 will start sometime in March 2011.

But until then, I should point out that season 14 isn't actually over yet! It's still got 7 more episodes to go, and the first one will be shown on October 6th.