2022 likely for all entertainment and the 50th. To be honest I wish WDW would just make a announcement for nighttime entertainment returning in 2022 so we all can stop wondering. Yeah it’s going to hurt to think we have another year to wait for fireworks, but having confirmation would at least kill the hope and wonder for this year.
I'm guessing they aren't announcing because they aren't certain.
Though I don't think any *significant* entertainment return is imminent... they probably see a window of starting to bring more stuff back anytime between summer 2021, and early 2022.
If I had to bet, I'd even say Harmonious could come this summer. (1.. social distancing is easings at World Showcase... 2... Epcot could really use a night attraction right now to actually draw people to Epcot and to help the restaurants around World Showcase).