How many F-16s and F-15s were upgraded with GaAs AESA radars? How many got GaN radars?
Good question. I honestly don't have a clear answer for you other than to say that I know that they have been working to deploy AESA radars to F-15 and F-16 over some time. You could even have a combination of GaA and GaN depending on when the radar was introduced.
Overall, I suspect that within the next several years they will all or nearly all be GaN AESA radars across the F-15 and F-16 along with the Eagle Passive Active Warning Survivability System (EPAWSS) for the F-15 and the Integrated Viper Electronic Warfare Suite (IVEWS) for the F-16. Outside of that, ~600 F-16's are to be upgraded to the V standard configuration over the next several years.
This goes to show that they would have quite an inventory of aircraft that could be converted to loyal wingman and be capable of performing numerous roles. I see no reason why these 4th gen aircraft should be discarded or sold off when they are likely more capable than any loyal wingman yet built.