It's been a while since I played that game and I read they might change(d) it.
But how it would work is that if e.g. xpac content would be added, it uses a separate character level, talent, and gear system. Whenever you're in vanilla continents (EK+Kalim) you have your standard level cap of 60 and vanilla gear.
But once you go into e.g. Outland, your character level is set to 1 and your gear changes to your empty starter gear. Quests will need to be updated from 1 to 70 instead of 58 to 70 ofc.
Once you visit vanilla zones again, you will transform back into your (max) level 60 character with the gear you had then. So it doesn't invalidate old content, since you can still progress in it.





