Tim will NOT be Jason. Derek Mears, the man who played Jason in the reboot, is confirmed to be coming back. As a fan of Platinum Dunes, the company behind rebooting Friday the 13th, I follow their blog posts, as well as Brad Fuller's Twitter, and he's already confirmed it some time ago.
Besides, work on the next installment of Friday the 13th hasn't even begun. Platinum Dunes just barely wrapped up filming on the Nightmare on Elm Street reboot, and they are in cutting/editing stage now.
All of this information has been divulged by Brad himself on the Platinum Dunes Blog and his own personal Twitter.