while that's true - you can't increase the number of tourists indefinitely. There are limits to infrastructure (airports, trains, hotels, restaurants). Therefore travelling long distance or to popular destinations will get way more expensive, and people will explore more outside of the popular destination or will travel closer to home.
Absolutely, yes. Medieval cities have an upper limit to them, and that upper limit is fairly close. (Already exceeded in Dubrovnik.)
We will see high tourist taxes introduced all over.
I wonder if the cities blessed/cursed with an enormous influx of people willing to pay high tourist taxes just to see them will develop something akin to "Dutch disease" = basically stagnation and corruption based on certain income regardless of quality of governance, which disincentizives competition, learning, investment etc.
The original concept of Dutch disease is based on resource-rich states, but being touristically attractive is a kind of "natural" resource too. As long as places like Rome can prevent street crime and keep the monuments from falling apart, the crowds will come, even if the local town hall consisted of mediocre politicians.
Mafia is also known to prey on tourist establishment. If the main lucrative attribute of your pizzeria is that the guests can see Colosseum from its windows, you cannot move your business and are forced to pay whatever protection money they want from you.
