"Mixed bag" is the phrase you're looking for regarding the other answers. Nitschke said that future M engines "at the core of their architecture" would "be closer to BMW AG engines" that are optimized for M cars, instead of following in the line of unique marvels like the V10 and naturally aspirated V8. They will keep the high redlines, however, with Nitschke saying "there is room beyond" the 7,000 rpm mark in BMW's current V8 turbos.
Managing weight will keep the same priority for M that it is for every other brand, so electrically assisted power steering is coming, as is an "unconventional" materials mix. At the smaller end of the M scale, Nitschke described three-cylinder engines as "attractive," saying that the brand can produce more than 310 horsepower from a three-pot.
As for the current M3, it's all gone. Nitschke said the company has about six more months of coupe and convertible production, but the units to come already have customers "on principle."