Its only one data point, but there were pickeball courts installed about a year ago in a park along one of the bike trails I use. 7 or 9 of them, I can't remember how many. I rode by one day, and they were all in use. I was astounded. Came back about 75 minutes later and there was still a gathering there. Now, they're not always being used. I don't know if it was a league or maybe it was a group function or something like that. But it does seem like they are popping up all over.
There are 2 courts in a senior living community along the bike path in the other direction. Its common to hear the sound of the racquet and ball as I go by. Not every time, but frequent nonetheless.