Loot reborn was revamping gear and loot. Infernal hordes season added the game mode. The Realmwalker was not well received. It could have been if they improved upon it but they did not.
So we go back to powers. Coming up with new game modes to base a season around probably takes some time. Powers are easy. You just think of some random thing and create powers for it.
We are most likely going to see more powers seasons than not. They need to save expansions for new features.
Season 15. Balance reborn. Would be nice and received well by all. Balance your game.