That will never happen. The extra money BMW will get, they will not spend on M vehicles and supercars, they will spend it on other ways of making even more money. And this will go on and on, other wise we would already have our Z2 and our M10 today. It is already a decade BMW is promissing us these cars. But that is just to keep us dreaming and buy their current cars until those we are craving for come. But they'll never come. BMW's supercar (a.k.a R8 rival) is the i8 Coupé and BMW's small fun-car (a.k.a GT86 rival) is the i3 Coupé. That is all we'll ever get.
I hope they get the M2 and M4 right, that is all about I care.