I mean, forever.
It looks like that's the game plan.
Powerful bonuses for multiple True Reincarnates combined with exponential stacking xp penalties as you go. Designed to keep you grinding out the entire 1-20 level range over and over again, as opposed to being ready for new endgame content.
The completionist feat. A delusional suggestion that you should actually do this grind a minimum of 11 times, and should a new class come out, do it again (probably twice again unless you are totally in love with whatever class comes out).
Constant revamping of old quests in lower and mid level range.
Recycling quests into "epic". Zero base XP. Unlike previously where we had a frozen amount of xp at the level cap its "maximum xp achieved" and the extra four AP automatically awarded.
True Reincarnation cap would have to be raised as well...lol.
Are there plans to ever raise the level cap beyond 20?