They are not going to use the N55 (or varient) in the next M3. The design of the N54 and N55 mills doesn't have the tuning and reliability creds they need for a e9x M3 V8 beater.
Pretty sure it will be a 8cyl TT putting out less than the nextgen M5 version.
2008 BMW e90 M3 6MT
1990 BMW e30 325i 5MT