One thing I've maintained (and I believe has been proven true) is that the Murozond we encountered back in Cataclysm was not the future Murozond of
our timeline. The timeline we went into during End Time wasn't even that Murozond's "home" timeline either. Since it was established that the Murozond we encountered was "outside of time" at that point it is technically unclear which timeline he hailed from.
I think that the Murozond we encountered came from a timeline where the "fate worse than End Time" (
"I have witnessed the true End Time. This? This is a blessing you simply cannot comprehend.") occurred and he knew (or at least, thought) that the same fate was going to happen to our timeline. So he instead lured us into a different timeline where the Old Gods had succeeded in causing the Hour of Twilight (with Deathwing impaled on top of Wyrmrest Temple) and claimed it to be a far better fate than what he had experienced.
And as the expansions have gone on and the cosmic scale being brought before us -- even with the Jailer saying we must stand united against "what is to come" -- it seems ripe for Nozdormu to potentially see a far worse fate to happen than the Hour of Twilight.
TL;DR... if Blizzard decides to continue that story (so far removed from it now though, I don't think it will have any real impact) they are still within conditions of their already established lore to do so.