When it comes to human infrastructure, it will always be able to be improved and have the ability to adapt, as our technology will continue to advance and to be able to accommodate and improve. Tourism really isn't going anywhere, and only a few nutty deep green people even suggest this.
Tourism generates numerous alternative means of transportation in many areas, which benefit residents. The tourists themselves also fund much of the infrastructure. Generally, tourism doesn't stop unless something serious occurs to hurt tourism to a particular area, however this is generally short-term, thus long-term funding for infrastructure generally remains. The only reason that infrastructure strains caused by tourism would be unsustainable, would be if the gains from tourist dollars were not put to use in infrastructure.