Frost is a hot name right now, that doesn't come around often in a coaches career. You strike when the iron is hot. Frost would be taking an enormous risk to wait until 2021 to leave UCF and stay at essentially a mid major. What does he gain from that other then fulfilling his contract to UCF? By then, Inevitably he's had a few losses on his record, which will be seen as mid major losses, he won't be a hot commodity anymore and his name won't be on many openings.
I think Frost is a great coach, I wanted him in 2013, but the longer he stays at a mid major, the greater risk his stock falls.
to keep this on topic of if Riley stays and not let it run into a frost thread, I'll say with next seasons schedule with Riley we go another 5-7 season and we are further into the hole. Also with Riley returning you won't see much excitement from the fan base this off season and into next year, because we all will figure the outcome of a 5-7 type season. The sell out streak will also be in great danger of ending,