I believe I have answered this question already, but please let me elaborate more.
Migration has two dimensions, technical and licensing one.
Technically, it is no problem to move your management server to a new platform. However, you are right, the out of the box MGMT licensing only allows managing up to 5 physical FWs. This concern is also applicable to your older management environment. Where, I believe, you have some extension in place.
Hence, I would advise you to raise this with your local Check Point representative. He/she will help you out.