More playable heroes each year? I might be getting my hopes up, but here are the facts I've seen.
hero powers will scale by level, which means a more balanced experience. This was also said to help streamline the hero creation process (I'm assuming because there will be less power tuning needed over time)
uniques are going away and being replaced by omega gear, which will greatly reduce the time needed to create hero specific gear.
permanent size increase/decrease visuals are being removed to lessen the load on hero/costume creation.
with the difficulty slider coming, this could mean less zone/enemy tuning (once they are balanced appropriately; I'm looking at you ranged mobs!).
There seems to be one common theme with all these changes: streamlining and simplification. I can only hope that these changes allow the devs the time to release more heroes and content. I'd love to be able to hope for some of my lesser-known favorites becoming playable someday!