Seems to me that if they flipped the gear up they'd be able to tack on
another twenty knots, since that's what a (good) cutlass gains over a
172.

Sounds about right. However I doubt Cessna would build a new plane with
retracts for liability & maybe cost reasons. Cirrus and Lancair have
shown that FG can go fast if the airframe is slick enough. Maybe that
300hp Bombardier turbo V6 might end up in the new plane. That would be
quite a combination IMO.