The end game doesn't exist because it's an MMO. End game is when the playerbase dies out, but it will never happen. Lucky to us!
End games are usually for games without an open ending. End games are usually lore packed, but WoW hasnt finished "writing itself" yet.
I don't think they would end it as far as releasing the game is concerned, since it makes them more money.
I dont think we will see an end to WoW. I mean I have been playing WoW for over a decade and thegame keeps evolving.