Let's see:
We have lots of unresolved plotlines. Who is the "she" that is mentioned in all of the Old Gods' prophecies? How will Azeroth be healed? How will the Horde vs. Alliance war be resolved? What are the five torches and the five keys? What were Anduin's 3 lies? Will Derek successfully integrate into the Alliance or will his programming awaken and force him to kill his family? What's the deal with Calia and light-raised Forsaken? Who is Bwonsamdi's boss? Who brought Vol'jin back? What is Sylvanas' endgame?
The fact is none of it really matters. The Alliance and the Horde will team up to blast N'Zoth in a single anticlimactic battle and that will be the end of a 17 year old Old God plot. The factions will then unite and that will be the end of it. All of the prophecies, plot hooks and mysteries will be conveniently brushed under the rug and forgotten about. There's just not enough time to explore all of that in 1 patch. Just like there wasn't enough time to explore all of GoT's mysteries in 6 episodes so the writers just kind of forgot about all of them.
If you need any further proof, just look at 8.2's "story". It's like Blizzard hired Dumb & Dumber to write it. "Well, the Alliance and the Horde kind of forgot about the Tidestone but Azshara sure hasn't forgotten about it..." And the war campaign wastes valuable screen time on Baine, Thrall, Saurfang and Jaina being SAD about HONOR instead of moving the plot along.