This is just something I've hoped/thought about for a while now. Feel free to hate it
As a future plot down the line. We learn that its not good for Aurene to just have to many magical domains, so they try to split things up using some machine Taimi made to transfer the magic essence of Mordramorth into the Pale Tree to boost her up to be the a new nature elder dragon and so sylvari can start to be born again(since they never really got into if new ones were blooming and stuff it be a good excuse for them to transfer the magic in order to save the sylvari race from going extinct.)
It works, BUT because its a big amount of magic something goes wrong and POOF God King Joko pops out and has all of the death magic power of Zhaitan and god magic power of Balthazar that was in Aurene. Then he is the new big bad for a whole expansion. They could even use this plot line to restore the six from now being the five as well if they used the Sword of Balthazar(which they kept around very deliberately in season 4) and some device to suck out the god magic inside of Joko to weaken him, and then elevate someone else into a god like Zafirah.
I would assume in this storyline as well this could take us back to Orr cause its super undead and its still got a lot of room for maps, so maybe the end could be us killing Joko and replacing him with Trahearne, and yes I know he is dead, but I think that is why he'd work so well as a replacement for the elder dragon of undeath. Trahearne tells us right before we kill him at the end of HoT that we need to kill him with Caladbolg because it is connected to him, that he's bonded to it, and only it has the power to free him.
Now if you think back to the personal story at the very end when we pushed into Orr, Trahearne stabs Caladbolg into the heart of Orr to help purify the land infusing it with its essence, so in theory this could mean a chunk of Trahearne's soul could be infused into the heart of Orr. This would also allow him to finally fulfill his wild hunt, since it wasn't to kill Zhaitan it was to cleanse Orr. If he became the new Death Elder Dragon then he would finally be able to do that by taking control of the Risen.
Anyway that's just my idea for a cool story in gw2 o-o