Cutting back MIA and SJU frees up 737's, am I correct?
738s do not fly to SJU, and as of now the only things that have been announced for MIA are increased service; not cuts yet. Considering it's a high O&D operation, I wouldn't expect much cuts from MIA, nor JFK and LGA.
738s do not have to be free'd up, because more are arriving starting in January...34 to be exact.