We're already down to 1 new dungeon per patch now and it's usually reserved for the MSQ. which means it will be a very scripted experience. As the game has been going for so long now, the devs feel the number of existing dungeons has become very large and would like to think of new player experiences instead.

Everyone keeps asking for mythic+ type system to be added. dungeons are too much work to re-work which is prob why the new "Unreal" trials are being considered. but even then only for limited time periods and limited amounts. (one)