Xbox 360 is selling well in 2011

They probably won't bring a new system out for another 2-3 years. I think that now since the system is profitable, microsoft will milk it as long as they can. Plus there are still some advancements in graphics engines that can keep the lifespan going (Unreal Engine 3, Crytek Engine 3).

 

http://www.industrygamers.com/news/xbox-360-ships-137-million-units-in-fiscal-2011-profit-doubles/