Probably been a while since I reminded you guys that Warpaint owns, so hey, Warpaint owns, y'all!
Why people is assuming that the expansion ends in 5.4? If I remember correctly, Blizzard said that they wanted to speed up the patches launches (ha ha, that last sentence sounds fun), with shorter waiting time between launches and smaller patches like in Vanilla. Couldn't that mean that we could end in, perhaps, 5.12 or so?
Well, the expansion tends to end when we take out the final boss, and in this case Blizzard has been very clear: Garrosh is the final boss, and we fight him in 5.4. It's a reasonable assumption that's when the expansion will end! If it doesn't, the following patch will almost certainly not be a major content patch.