What is the E90 series going to be powered with, the non-M version?

Is there any truth to the floating rumor that they will drop in the current S54 engine detuned back to around 315 hp, or maybe drop in the S54 engine as it sits into the E90?

I mean, there would be such a HUGE discrepancy from the 330's 225 or even 235 hp engine (pp package) to the 400 hp monster ///M. I thought I read somewhere that BMW might just drop in the S54 I6 ...

Perhaps that would detract from ///M sales though?