Even though a power dome on the F80 would probably not be required from an mechanical point of view like on the E9X, I agree that aesthetically it would be awesome to keep that tradition going - I love the powerdome on our E9x M3s!!!
Even though the test mules for the F8x M3's do not have powerdomes - the fact that the turbo I6 or turbo V6 does not need a powerdome would be entirely consistent with BMW not having it on the test mules (i.e., not necessary for it to be there for testing purposes, but would seemingly be an easy, final "production modification" once all testing/mechanical specifications/components are finalized).
The renders of the F8x couple/sedan with powerdomes look totally awesome