The huge drop off had already begun and will accelerate. The question will be how low the case count goes.
Of course, it's largely the vaccine but not entirely. We had massive declines last April/May. It's hard to appreciate because we were ramping up testing nationwide at the same time cases were declining.
But if you look at the March 2020 hot spots (the Northeast, Michigan, Louisiana), By summer 2020, Covid was almost non-existent in New York, only to come roaring back in the fall.
So the current decline is a combination of the vaccine + seasonality. (I do believe when we examine this in hindsight, there was a whole lot of seasonality in play).
The danger is going to be a fall resurgence. But with a high enough level of vaccination, we should be able to avoid any significant fall resurgence (and the south when through a late summer spike in 2020).