Originally Posted by
Jokubas
I'll fully admit I was wrong about what Legion might be, but I remember a lot of people guessing what we got. I remember a lot of people saying it after Mists of Pandaria, after the whole Wrathion thing especially, and Warlords of Draenor did hammer that in.
At the same time, it's only as obvious as it seems in hindsight. The final cutscene was frustratingly vague and there was a lot of debate about it back in the day. We had no idea what "pact" Archimonde was referring to, and Gul'dan did not seem happy about getting tossed into that portal. Since it's also the portal that Archimonde emerged from, implying it went to the Nether, a lot of people speculated that Gul'dan was being punished for failing as part of that pact. The idea that he'd end up on Azeroth and open a portal for them was certainly not a given.
Gul'dan's staff fading away implied he was probably still alive, but Khadgar commenting that he and his masters aren't so easily defeated was a bit baffling at the time. We didn't have the whole lore about alternate demons and easily respawning demons at the time, so it didn't make a lot of sense. We just trashed Archimonde, one of the toughest demons, even faster than we did the last time, and even in-universe most of the characters didn't know the demon lore yet, so it was a weird thing for Khadgar to say that, so no one could really be certain as to what he meant.
Finally, we had Yrel say that if we needed their help some day, they would come. That kind of dialogue isn't usually reserved for the immediately following plot (not that they have come to help us, but what we would call their help for came immediately).
On the other hand, there were a lot of other unresolved plots or orphaned references. Ephial's mysterious allegiance still isn't known, and Cho'gall's last words warned us of someone coming (that would, in hindsight, almost certainly be a Void Lord). Then there was the shipyard system, which included several new ship models for what was a relatively throwaway system without significant relevance. While that certainly isn't a cliffhanger, it seemed like an odd use of resources if it didn't lead to anything else.
Not to mention that many of these things were not considered mutually exclusive. For instance, while Azshara's current loyalty is to the old gods, she tried to let Sargeras into Azeroth before, and it wasn't completely unreasonable to expect that Gul'dan and Azshara would help bring about the invasion that was implied at the end of Warlords, still giving us the calm before the storm while ultimately fulfilling the cliffhanger.
As for next expansion, there have been several other guesses. If you can find some threads that predate this, South Seas wasn't even necessarily a major one this time. There has been a lot of expectation to see the undead on the move. Someone made a good list of Bolvar's actions, updated undead models, and odd happenings in Northrend during Legion.
Even earlier in this thread there have been some alternative ideas offered. It's just that datamining a file with the quest naming scheme referencing a specific area narrows down speculation in a way that story guesses can't.