There's no money left on the table if they switch to pre-packaged desserts like they did for Fantasmic- in fact, they'd save money. It would take less staffing and less food. Not a chance they'd reduce the price just like they haven't with other buffet meals that are no longer buffet. I think it's going to be a good long time before we see buffets like we use to, easily one of the last things to come back- if they ever do.
At this point, I think they could get away with just selling tickets to the garden viewing area- make them a special add on. I guarantee you, they'd sell out every night, desserts or no desserts. I'd be one of the first in line to buy. But there's more money to be made if they sell it as a dessert package and I think that's what they'll do. At least I hope so!
I can't imagine they won't do something and quickly. They are very good at bringing back things that bring them revenue.