You can hear the claim in the March 15th FastLaneDaily episode:
Fast forward to 1:30 for the claim
Their claim is that Nitschke has confirmed a 1M successor and that it will be based on the F20 M135i. Although it sounds like the latter part of that information is based on their speculation, not the cited source.
I'm thinking they're probably wrong and Nitschke is talking about the M2, not an F20 based successor. Anyone know any different?