Originally Posted by
LastBlood
Six new playable races, including models and 1-85+ experience.
Multiple new battlegrounds added for every level bracket.
Updating of the original races as to not tip the popularity scales in favor of the new faction too much.
Redesigning every, or at least many zones to put in new bases and camps for the new faction, or introducing an entirely new continent (or something similar) where the new faction is offered a leveling experience with contested zones (meaning Horde and Alliance will need to be able to quest there as well).
This is just what I come to think of without going too far into the subject. We're not talking a Cataclysm size revamp here, the project will need to be much larger than that. If they don't have it as a side project, any other expansion pack will be delayed for years. If they do have it as a side project, they'll just need to add more and more content until they've finally reached to a point where they've caught up, and that will take even longer.
It cannot happen.