I actually agree with some people here, and think that the new races (likely only 4....they will hold one back from each side since the Zandalari likely cannot come out until BfA) are going to be the "stop gap" measure to keep people here. There is a new riddle to solve, the hardest ever (get your pet from the Many Face Monstrosity or whatever it's called.....the little girl dranei pet is supposedly going to play a part in it), leveling is being made "tougher" (more xp needed, mobs have more life and hit harder), and the new races are going to be tossed in for good measure in order to give people at least a month or two's worth of content. The fact of the matter is, they have clearly said late 2018 for BfA. That means we are in for yet another 1 year content drought. I have no idea why a company would continue to do this after years and years of complaints about it, but hey, I just play the game.
I think we will see the new races for people to level and whatever the pre-patch is for BfA and that is about it.....for a year. This is why I unsubbed last month and plan on staying unsubbed until February or so. That gives me plenty of time to grind out the Seat of Triumverate, grind for pets/mounts, level the new races, and play other games leisurely without rushing through. But it still will only be 3 months tops. Which means people like me will likely unsub for most of this year unless there is a "stop gap" patch with a dungeon or something. Something in line with the WotLK patch at the end with the new raid and dungeons...