I won't speculate about what will happen but, based on looking at the Publix booking system for FL today, it's not unlikely to see areas top out at that percentage. With 40+ eligible starting today, there are still appointments available in Bay, Escambia, Leon, Nassau, Okaloosa, Santa Rosa and Walton Counties six hours after the booking window opened this morning.
These appointments are just for Moderna and FL seems to still be getting the same amount of that vaccine per week (208k first doses) as have been delivered for a couple of months now. Other than some system issues, I didn't have that much trouble booking an appointment in Broward for my brother this morning even though Broward and a lot of the larger counties filled up within two hours.
It does seem to be an indication of softening demand which is why I believe that it is imperative to give incentives to people who get vaccinated and allow them a "back to normal pass" after they have reached maximum protection. Regardless of certain political beliefs that may lower the acceptance rate, it is going to be very difficult to convince over 60% of healthy people in their 20s and 30s to go through the hassle of getting vaccinated without a reward for doing so.