I guess we'll need to wait and see what Dinan and others can coax out of the m40. With the new Z4m40 at 386ish(?), if Dinan can get another 30-40hp out of it, that should move pretty well.
With it being less $$ than a true M, that might make most folks content. Though considering the Boxter S is 350hp from a 4 banger, I don't see why they couldn't have done a little better.