This is interesting for several reasons:
1. The current M5 is very new, so one must ask why BMW is telegraphing it's intentions for something relatively far in the future.
2. If the M5 will not have a manual transmission, it is reasonable to assume that the entire 5 series will not have one either. Note that except for strengthening the unit, all the other above mentioned problems will apply.
3. One must ask, exactly what is different about US customers that makes them want a manual transmission when nobody else does. Beats me, and I live in the US.