Looks like porche is coming to forza 4
http://forums.forzamotorsport.net/forums/thread/5247653.aspx
It comes: First details of the Porsche Durc expansion pack ...
While the Forza Motorsport community currently turning heads on the next open world racer Forza Horizon, may in the near future, apparently, Porsche fans finally breathe again. Having already been seen in the Horizon-trailer vehicles from Zuffenhausen, today we learn early on that soon, a comprehensive Porsche expansion pack for Forza Motorsport released fourth
The expansion will include a whopping 30 models of sports car manufacturer and racing 20 new events, which provide players with an additional 250 Gamerscore points. In addition, the expansion pack to be released Porsche already within the next three months. About the price is yet unknown.