Makes sense. The next M3/M4 is supposed to be a stronger variation of the N55 (forged parts perhaps?). M2 will need to refrain from cannibalize sales/competing with the M3/M4. The current 1M is too much on a par with the E9x M3.
That said, BMW will probably squeeze 350HP out of a turbo 4 cyl
... thing is it has to be more power than the M135i