In some way the new Porsche 911 (991) will be the new M3 rival, and a very, very tough one. Plus to benchmark performance (straight line) and handling (curves), it will be the best looking 911 ever, the most refined, and a very good daily driver. Then 3 months after the M3 F32 release, there comes the new C AMG, powered by a new ~3.5l V6 Comprex Supercharger. The RS4 will get an upgraded version of the 3.0l V6 TFSI (supercharged), larger displacement is possible, as we saw with the the new Audi W12.
What is sure, is that BMW M has to work very hard on the new M3 F32, and NOT think to much about costs, as they did with the 1SMC, because now, the M3 is loosing its value, due to very tough rivals (C 63 AMG, RS5, IS-F,...). VW may also bring out a new Passat R, powered by Audi S4 engine. And I am also thinking about a new Jaguar that will replace the S-Type (XS?), and its sport model (XS-R?), as the XF-R rivals the M5.
I think the M3 has to focus on cars such as 911, R8, in other words the supercars.
RS4/RS5, C AMG, IS-F, XS-R,... < M3 < 911, R8, R4?, SLS, SLS Baby?, Lambo, Ferrari,...
If M does a mistake with the M3 F32, it is all over for M, and so for BMW, even with BMW i and MINI.