That window is definitely closed now, mostly on Rossi’s side.
For the same reasons that Pedrosa chose to retire as an HRC rider than ride a Yamaha.
Rossi is very valuable to Yamaha and Vice Versa post retirement. They are going to make each other a lot of money for years, maybe decades.
I agree that it is not going to happen (HRC/Rossi) but that would be marketing coup to take one of the greatest from Yamaha their nemesis.