You mean MS would dispute using the license for W7 again? I feel sorry for those who are entrusting their machines to MS at this point. I have had two encounters with Win10 - on my Win8 phone and in the Win10 Insiders program. On both I've tried to get off their spam lists, and found it impossible both times. Under the subscription model, MS really wants to hang on to people tightly. I'm glad I jumped ship.
But as for most Win7 licenses, they're just generic OEM certificates and keys, so I think restoring by image would fall under their good graces automatically.