Is it actually possible for them to keep adding content without raising the level cap

[Garnatian]

It negates content and removes peoples work.

Would you rather have 16-20 different things that are worth doing at endgame or 2 things that are worth doing after 2-3yrs in a mmo. It is the difference of being able to play 70hrs a week and not get bored and be able to do all valid content every week in 8-10hrs. It allows a game to be truly endless and give everyone no matter your playstyle enough content to continue subs for an indefinite time.

Level increases have almost no positive attached to them besides removing the currently players hardwork to remove the gap between new players and old... which to me is a horrible way of doing it.

Game should not be at 50 for long...but next few level cap increases they should just raise it and leave it there for the remainder of the games existence.

Negates content? What? That doesn't make any sense. Gear itself will negate content, not the levels.

All it does it provide a progression "reset" which allows new players and casuals to feasibly catch up with end-game players so the cycle begins anew.