The Plague is in the past. After Shadowlands, bringing it back would be a bad joke.
A new Plague of Decay would be another thing, though. We all know Decatriarch Wratheye from DF and how she escaped.
I don't think that Iridikron is peacefully resting during TWW. He is probably mastering the Decay Magic that he extracted from the body of Galakrond with the Black Heart. In Dawn of Infinite, he says: "A hunger lost to the ages. One which I shall reclaim!". So basically he wants to become a new Galakrond.
Iridikron is probably building an army of Decay. He can raise anything that he wants, and he has plenty of bones in Northrend. Now that the Dragons have mostly returned to the Dragon Isles, no one is going to stop him there.
In Midnight we will see the first appearances of his army. The Amani will be overrun. It would be a similar situation like the one we lived in Northrend with the Frost Trolls. We will cleanse the Amani forests of this new Plague, saving the surviving Amani Trolls in the process.
The Decay Plague will also be present in Lordaeron, and of course the Scarlet Crusade (heavily teased in the past two years) will be doing their thing and we will have to stop both of them. I would not discard that the Arathi integrate the Scarlet Crusade in their army. Probably they have similar zealots in their Empire, and us fighting the Scarlets could be the first point of friction with the Arathi.
I can see a very different Northrend, with at least the following:
- Two underground zones (Azjol-Nerub and Harrowsdeep).
- The surviving Azjol-Nerub Nerubians will be confronting the Decay Plague, but this time their cousins of Azj'kahet will come to their aid.
- The Earthen of Northrend and the Earthen of Khaz Algar will become allies.
- There would be a full Dragon war between Iridikron's Decay army and the Aspects forces. Similar to the War between the Blue Dragonflight and the rest of the Dragon forces in WotLK.
- The Djaradin, the Harranir, the Arathi and the mysterious Vrykul of Siren Isle will be present.
- Regarding the Titans... Is really difficult to speculate about them until we know why they come to Azeroth. One thing is certain, though: Illidan and Sargeras will be free.
Changing the subject, I see some speculation about Kel'thuzad. Please stop. He is not coming back. It was a little cameo in the anniversary perfectly resolved in those quests. It would be pathetic if Blizzard brings him again.
We have to move forward. Characters like Thrall, Jaina, Sylvanas, Tyrande, Malfurion (this one especially) have become jokes, and the best service that they can do to the story is dying with some dignity. Thankfully Blizzard is presenting a new generation of characters that will eventually replace some of them.
BTW, good work with Delves in Season 2 Blizzard. All the changes are fantastic:
- The totem for the venom is now easier to handle.
- The underwater Delves feel much better now that we don't have to care about breathing.
- The difficulty adjustments are perfect. This is a feature for casual players and it should have a casual difficulty.
They will need to do something with raids and dungeons, because I can see most players just doing Delves (like myself

).