Great Question! I did some quick checks and between the Motorsport Magazine database and Racing Circuit info there are 931 real world venue's listed: many have multiple track-layouts and historic versions.
Between AMS, AC, ACC, iRacing, PC2, R3E and rF2, 173 of those venues are simulated (again, many have multiple track layouts and historic versions) and that isn't counting the many mods. Older sims also have still further venues.
All that to say that indeed we are already having a very rich choice already.