Some interesting infomation from Autocar regarding the 997TT
It appears it will be powered with a reworked 3.6 engine generating 460hp. More interesting is the paddle tranny and the e-differential ala Ferrari. 
http://www.autocarmagazine.co.uk/news_article.asp?na_id=212046

http://www.autocarmagazine.co.uk/news_article.asp?na_id=212046