I just made camping reservations for Yellowstone for next summer. I thought, I really won't want to go anywhere where there are crowds. Even though Yellowstone gets a lot of visitors, they're spread out over a huge area. Your campsite is several yards from the next one. If anyone tries to get too close, you can repel them with a flaming marshmallow. And of course, daytime activities can be as solo as you like--great hiking there, as well as scenic drives. Stay out of the visitor centers!
I also checked with Parks Canada to see about a camping reservation for Banff--in the past, by this time of year, just about all campsites were already reserved. Good news--there's still availability in June. Bad news--they're not taking any reservations at all right now. All Canadian national parks are closed until April 30. There's also a general travel ban there right now, but that does NOT apply to Americans--yet.
So I may spend my vacation in the US Rockies, where I can practice social isolation easily enough. I don't think I'll want to visit any major city, or any attraction where there might be a lot of people in a small space.
I am, of course, making the assumption that the coronavirus will be nowhere near contained by summer.