If Kevin Durant agrees to join, I think Wade takes a hometown discount to stay in Miami and finish his career there + to play alongside Durant while getting to finish his career playing for Championships in Miami.
The news around Bosh has been more hopeful lately. It sounds like he will return. Miami are giving medical info to free agents. They obviously feel that information is positive enough to convince FAs that Bosh is very likely to return. Strange turnaround from a few weeks ago but it does look like a situation that has changed.