Maybe I'm a bit late here, but a couple of thoughts I would like to share.
Aesthetically, and as
@Matski commented earlier, drawing conclusions on how the road going version of the standard 8er will be by looking at the GTE version is not the best method.
From the inflated fenders and the aerodynamic bodywork, the kidney grilles missing the slats (which I believe was intentional, as BMW did not want to give away more hints on how the 8er will look), the huge and complex rear diffuser, and the racing livery, all of these factors deflect from drawing a picture on how the G15 will look.
As for comparing the race version to the road going one on the previous models, it is possible that we have seen the standard production first, then the race car was introduced (in the case of the M6, the GT3 version debuted almost 4 years after the F13), but here it the opposite. Think of it as looking at the pics of the camoed cars and the renderings before the official reveal; you know they are close, but there is something missing.
As for the GTE car itself, I can see that BMW is being serious this time, by applyng the the "concave" front splitter and the swan neck rear wing. I hope they can deliver, and become a force to be reckoned with on the 2018 season of the FIA WEC and IMSA Weathertech chamiponships.
On a side note, I wonder about the current state of GTE class in general, but let's leave this for another time.