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

[Reslin]

I had read that yoshi didn't want to raise the level cap, and that approach to the game would interest me a lot more than having a raise each new expansion and making older content unused and ignored.

If they keep going with item levels, and stack content based on item level, add quests that are accessible based on item level etc. it could get pretty interesting.

How do you guys think they'll handle it?

City of heroes did for years. They lasted a good 8-10 years. The only reason the game died was due to issues in their management where many of their big time developers split off to do other things.