All V6's from now on, which is the future I guess, smaller capacity, more turbos, electric motors and better economy. I imagine performance won't ultimately suffer either.
However, I bought the current outgoing S6 purely because it's a V8 and will most likely be the last of it's kind.
There's no substitute for the rumble of a V8 when you hit the start button (bar a V12!).
I'm growing to like this S6 so much that I find myself reaching for the keys of it over my SL almost all the time. The engine is the reason.