I know it takes crazy amounts of time to create new courses/worlds, but just wanted to throw Washington DC out there as one for the future (that is if you are legally able to render the monuments - if not, it would not be worth the time IMO. I like Richmond but I miss the monuments not there though can understand why). It would be cool to run around the Mall area and surrounding regions with different paths. So just wanted to throw that out there.
I think new worlds are going to be focused on UCI World Championships now that they are officially tied together starting in 2020. So, Switzerland will be 2020 and Belgium in 2021. Look for Yorkshire to squeeze into London world this year (August/early September)
Adding DC (like White House, Washington Monument, Lincoln, etc.) would still be a lot of city. In expanding New York, I would not expect more city (Empire building, Brooklyn Bridge, etc). I would either think of an escape to the Catskills or an underground subway system for a pure flat addition.
However, if the next President is a big Zwifter…