The 4.8is replacement will be V8 turbo (or bi-turbo if its ready by then) with HP anywhere between 400-460. Doubt it will be manual, we don't even have the manual E60 M5 yet(I know its coming). Will be lucky to have the DCT/ZSG from new M3. But X6 will be more sporty with V8 bi-turbo and dynamic x-drive. Expect late next year and it will be followed by hybrid X5 in 2008 and X6.
More info here