So the latest rumors from Jason, are that the F8X's engine will have a 8.000 RPM redline? From an I6? That is just not possible on the base of the N54/N55. And 8.000 RPM would make alot more than the rumored 430 PS. It would be in the 470-500 PS ballpark.
We had the "spypic" of the "M3 F80"s engine bay. For sure this could pic not be taken by spy/paparazzi photographs. So it must have been taken by BMW themselves. What proves us that this car was an M3 F80 or that this M3 F80 was fitted with the engine that would go into production? They quite possibly gave that pic to silence all the V6 rumors. TT 3.3l V6 alot makes alot more sense now. And what about the 430 PS I6 and the engine bay pic? What if it was just the next generation I6 and of the BMW 440i?
I wouldn't bet on anything, because anything is possible. BMW is about cost saving, so they'll chose the engine that saves them more money.
And now and image about of the concurence:
Audi: They have the Supercharged 3.0l V6, to rival the Mx40i. Next RS4/RS5 will simply just get the Turbocharged 4.0l V8. That is cost effective. To make a more powerfull (~450 PS) Supercharged V6 will cost more than to fit in a Turbocharged 4.0l V8, when they sell this engine in all these following cars: S6/S7 (420 PS), S8 (520 PS) and RS6 (560 PS).
Mercedes: They have a new Turbocharged V6 that replaces the old Naturally Aspirated V6. But that is no performance engine. Are they going to build a special V6 for the C AMG only? No. They'll do as they always did. But now the new C AMG will get a newly developed Turbocharged 4.0l V8 (two A 45 AMG engines put together in V) that is also to power the SLC AMG, likely the successor of the SLS AMG.
So both the next RS4/RS5 and C AMG are probably getting a Turbocharged 4.0l V8.
What about BMW? Could also be a possibility. There were initial rumors of a turbocharged S65, this give as a Turbocharged 4.0l V8. Same displacement and configuration for all the three german premium mid-class sedans/coupés. Sounds ready for DTM battle.
Until any offcial, not "official", info release, I wouldn't be to sure about anything.
All BMW decisions depend on the costs and long-term considerations.
I'd continue expecting the follwoing possibilities:
TC 3.0l I6 based on next generation engine, S54/S55 successor, in various output configurations for x35i, x40i, to M3/M4/X3 M/X4 M/Z5 M (?).
TC 3.3l V6 based on TC 4.4l V8, only for mid M cars.
TC 4.0l V8 based on S65, to with various outputs to power the whole range of M cars: M3, M4, M5, M6, M7 (?), X3 M, X4 M, X5 M, X6 M, and Z5 M (?), with the exception of M2, which in this case could get an I6, and not an I4.
Specualtions can continue.
Disclaimer: Sound of spy vids. Not clear.