Well I know it's a bit... too soon. Still, it's all around my head, and I feel like Warcraft Universe goes depleted of content. We've been almost everywhere, we've seen almost everything. Quite a few things are left to be seen. Surely they can be pulled over to as many expansion as they'll need to, but I just want to imagine a one huge expansion with a nice number that finally closes the franchise at least for some time.
Don't have and idea of the name, let it be World of Warcraft - the Great Collision.
So, presumably at the end of Shadowlands that will likely deal with Jailer\Father of Sleep attempting to consume everything, in process of the final battle with Death some cosmic-scale events will happen. For example, the balance of primal forces is broken, the "enemy of all" (Death) is defeated, and both Light and Void are unleashed into the world. Azeroth becomes a centre of grand collision. Two huge portal open - one leads to K'aresh, a world entirely drowned in Void energies, homeland of the Ethereals. Other can be a completely new world, a Light-infused, or it can be alternate Draenor, turned into bastion of Light by Yrel.
All this is a preparation for war between Light and Void. Light seeks to turn us into the Army of the Light, to fight the common enemy, Void is purposed to claim Azeroth the titan. Since Old Gods failed their mission, the Void Lords decided to take matters into their own hands.
In patch 10.0 we'll visit both worlds, choose our sides or try to stay neutral. Launch raid will be Light-themed. Yrel and a group of extreme fanatics of the Light will try to make us join Army of the Light by force and brainwash. We help Tyralion take her place and see that she was actually manipulated by Void that was masked as some Naaru and induced fanaticism into the very heart of Light, so all was nearly lost.
Next on, we see that Void is about to launch a massive attack and actually summon a Void Lord in physical realm. Also, there can be some smaller raid on K'aresh where we explore Ethereals culture, see the Void plane, etc.
In 10.1. Murozond appears, saying that he saw that we have no single chance to win this time, so all time shall be rewritten. Here we go into a new type of location for the patch - the Past Azeroth. That is actually a great raid where we go deeper and deeper into the past, at some key points of history. The raid may feature:
* First\Second War\Beyond the Dark portal. The Old Horde, Ner'zhul, Deathwing, Alextrasza (under control of Necros), finally we roll the time back to help Lothar, Khadgar and Garona kill Meivh.
* Battle against Galakrond, trying to prevent protodrakes from becoming the Aspects.
* The Black Empire, we help Keepers defeat Old Gods and their minions. Last boss - Y'shaarj, where we lose, but then Aman'tul appears and... you know. Also he tells us that we'll soon meet again for one last time.
*Finally, we get into some wery strange place, pure timelessness, where we fight the Infinite Dragonflight and finally Murozond himself. Then, we get some important info and reappear in our main timeline, right before the attack of the Void.
An important note. I think all this stuff with timetravel raid and Murozond can happen sooner, in Shadowlands. It can cover the lack of new zones at launch, and explanation of "I've seen the true endtime. This is a blessing compared to what is to come" may refer not to N'zoth getting free and not to Void Lord claiming Azeroth, but to the victory of Jailer. And "Aman'tul...What I have seen..." is about Death claiming everything. So that may well be not in 10.1, but in 9.2. Changes nothing, actually. Also this would be a nice theme change from various Death encounters.
Next is 10.2. The attack of the Void. Somehow they manage to open massive portals to Azeroth and begin to manifest an actual Void Lord to our realm, who is trying to corrupt Azeroth. Clear enough, the full might of the Void vs us and Army of the Light. One interesting twist may be that they actually manage to (almost) turn Azeroth into a Dark Titan, and we fight her as a boss, and cleanse her. And then, in the end we manage to push a Void Lord back into Void and close a black hole he ripped open on the planet.
But, is this truly the end?
Sure not.
10.3. - The Final Battle.
As we fight, energies of Light and Void that pour around, collide. And what happens when they collide? The Fel.
While we are occupied, the remains of Burning Legion, led by Tichondrius, are waiting. He makes contact with Azshara, who played nice and repentant role since 8.3. An irony - she was the one who opened the gate for Sargeras the first time... and she'll be the one who will to that for the final time. Dreadlords and Azshara create a portal that links Azeroth and Seat of the Pantheon. Since the collision of Light and Void create a huge lot of fel magic, they use the portal to launch it, destroying the Arcane energies that keep Sargeras imprisoned. The Fallen Titan breaks free and, using the opened portal, crashes like a huge fiery meteor, directly on Azeroth, in his full might and power.
So, the final patch and raid of WoW will be a sort of Armageddon battle, where we face off against Sargeras and his demons (and Azshara), our side empowered with Army of the Light, Titans and newborne Azeroth the Titan who was awakened and almost darkened by Void Lords in previous patch.
This will be the end of World of Warcraft, but not the end of Universe itself. We know that Anduin will lead Alliance into final battle against Void when he's old, and Illidan will become a champion of the Light one day, but for now we'll have an era of peace.
What's next? I imagine an epilogue expansion, the peaceful Azeroth that remaines cultivated and healed after the Titan leaves the core, we actually live on the shell, but it's okay. Titans depart to the Great Dark, we stay to live in peace. All the old expansions will be reworked to new graphics, connected in a single phased system, free to access and re-experience.
And it's always possible to add something when needed. But essentially, it's the end of the main plot. For now.