It's just tricky because just about everything they've tried to do outside of the main formula has met with mixed success or negative results so far. Hunts are and continue to be a mess that they seem to have given up on reigning in. Diadem's been a mess. Lords of Vermillion seemingly took a lot of resources and has been seemingly pretty unpopular. The Gold Saucer was pretty popular for the first month and is now largely empty most of the time. Triple Triad's largely died out in popularity as well. Treasure Maps were new but ultimately have ended up being an incredibly minor part of the game, which have varying levels of player involvement. Though not directly related when it comes to new content, their experimentation with difficulty in HW has been kind of a mess, too, and I suspect the team may be getting reflexively more conservative.
I think we'll still see one new type of content in Heavensward (perhaps in 3.3 or 3.4), but I imagine their main focus now is on getting the ship righted after the problems with 3.0/3.1.