That doesn't mean you can't look and see what is the most likely even if it doesn't happen. If it's a 2 tier xpac their options are very limited as it's going to be really hard to make a story out of something that doesn't exist in 6.0 (sort of like how the Blood Elf lore in MoP came out of nowhere, but they had 3 patches to build it up).
Also, while TI gave Garrosh the ability to start WoD, from the beginning he was going to be the device for launching the next xpac.
Here's what we know: 1. Final tier will be heavy Legion influence. 2. Cho'gall is playing with void stuff (though this story seems like it possibly will get wrapped up in 6.0/1) 3. Wrathion will play a part and there already are Bronzes working here. 4. In BC the Arrakoa tried to summon an Old God.
Also, and what perhaps narrows it down even more, is most likely we are going back to MU after this. That excludes things like fighting a Draenor Old God next xpac.
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It's called speculation for a reason. I've already given alternatives to Legion if it's not previously.
Naming and creating a Hearthstone expansion after a relatively unknown town in the middle of a non-popular zone that is shaped like a Horde symbol, not an eye, seems reaaaaaaaaaaaally odd and non-likely.
Naming and creating a WoW expansion after a very well known villain with lots of story, history, etc, as well as the name also having potential reference to an artifact or "eye of the storm" type events(aka hurricanes), seems much more likely.
Granted, both "work" and are possible, but I think one is way more likely(in terms of story/name) than the other.