Perhaps being from FL gives me a really jaded view on this thing, but I don't think it'll take much time for things to get back to normal in many parts of the country. I go to theme parks, the gym, malls, buffets/dine-in, have the option to go to sports games, ran in multiple races, and even been to Vegas twice since Nov. Always a mask, always try to maintain social distance, but other than not being able to go to Europe, on cruises, or packed-in concerts (there still is plenty of live music), life isn't that different than before.
I should note that I spent June-Sep in DC, as well. Was able to do many of the same things as last year (museums, casino, malls, Wharf) - just with modifications. Of course, late night bars/clubs really just weren't operating like pre-Covid.
So as far as basketball specifically, I can't imagine most games won't be selling out as soon as the 21-22 season. I remember hearing the acronym - CRAFT (can't remember a f-ing thing) - used to describe people/Americans several years ago and I think it'll apply here soon enough. For better or worse, once people are allowed to do things, they will - especially if they can get a good deal on Cs/Pats/Sox/Bs tickets.