Very true, it was estimated that the Supercharger actually uses about 60bhp just to run itself. Parasitic way of force induction, however its pro points of no lag and instant throttle response are well worth it in my mind.
There is much speculation regarding the configuration of the B9 S4, with lots of rumours regarding a new 3.0TT engine. I personally can't see why they would take an engine thats won and is still winning awards and suddenly replace it.
I remember reading that the engine developers, when creating the engine for the B8 S4 actually developed both a Turbo and Supercharged unit and decided the Supercharged unit was the better package. After a relatively short time, they get rid..... seems unlikely.
I suspect (and this is my thoughts only) that given the 3.0 TFSI engine has so much overhead in it, that they could continue to use it and bleed off less boost to give it the power increase that is expected. This along with the weight dropping by 100kg would probably be enough for the S4. The only thing they would really need to do is improve fuel efficency even further.. I could be wrong of course, but engine deveopment is not cheap and they are using the 3.0 TFSI in another applications, i.e. A6 and Q5, no reason to do so if they are to replace it.