Static NAT for RAP works in AOS8. It is incompatible with controller clusters at the moment.
If you deploy a single controller (standalone or under MM) or use two controllers with VRRP or LMS/backup-LMS for redundancy, you can use static NAT.
Having said that, if you have the same IP seen from the RAP, the same AP Group name on 8.x and the RAP white-listed on the new controller, I would expect the RAP to upgrade to 8.x and connect to the controller without end-user interaction. Please test in lab, or with another RAP that they connect properly to the new controller before upgrading many APs that are unreachable in the field.