I kind of want the next expansion to take place in the future. You travel there via a kind of Temple of Time where you use your Master Sword (Artifact) to power the device, thus explaining why you can't use it in the new expansion. When you travel forward, it would create a "snapshot" of your character, and there would be a statue of you in your gear in the middle of Dalaran, and probably in cities all over the world.
So like a full expansion of End Time?