We're going past level 100. So basically we can expect that every expansion from now to the end of WoW will have a level increase, because if they had one good chance to try an expansion with a different form of progression, it was Legion.
So, when can we expect to see our levels squished? At level 160? 225? 800?
It's going to get annoying, having to level characters through progressively more content to reach the the endgame. It can't possibly go on for as long as they can make expansions.