two faction seems to be outdated. but there doesnot seem to be anything that can change that (adding third faction, or splitting existing faction into two more seems too hard for MMO gameplay)
what if choices, that we are making, will make us choose between two brand new Playable faction?
imagine, that while questing we will have to choose between them. let's say, arm of the light and Forces of Old Gods
what if all of our characters will make decisions and we will play next expansion(s) as members of new factions, where both current faction playerbases will be split between these new ones (something similar to Pandaren player choice to go from neutral To A or H)
these new factions might wok similar to Order Halls. but instead of 12 Orders, there will be 2.
and most important - both Horde and Ally players will be interact with each other
some Orcs choose to worship Light, other Kaldorei choose joining Old Gods forces
would you like something like that?
technically it can give "end" to existing factions
and also make all players able to play together. and it will give more opportunities for storytelling