I ran my now-Epic party through
Bastion of Broken Souls as their last sub-Epic adventure, and at the end of it they requested as their reward that the beings in the Bastion release extra souls into the universe to save as many of the babies that had been born without as could be saved. They were therefore responsible for a sudden influx of soul energy into the multiverse, which lasted a full week before the beings shut off the extra flow.
I'm using that event as the basis for introducing Incarnum into my campaign world- it didn't exist before that event, but
after that event some people are learning to make use of that extra soul-energy that's floating around. There are plenty of souls, see, whose intended bodies died of starvation or thirst due to lack of their original souls before the PCs got the extra flow started. So now that soul-energy is bodiless- and it needs to go somewhere.
I also run time travel plots now and again, and there are two big ones currently in progress.
The first involves a complex situation wherein a sentient demiplane tries to destroy the world because of a prophecy that beings from this world will someday destroy it, and the PCs are gradually being set up to eventually confront this entity. The thing is, beings from the future wherein the PCs
fail to kill the entity can and do travel into the present multiverse, and sooner or later the PCs may end up in their home realm- one way or another. That would be a fairly major evolution of the world.
The second is my second group of PCs, who due to the intervention of a godlike entity from the Far Realm have been transported into the world of the distant past, from their perspective. They are now almost 1900 years in the past, and have already seen numerous changed things from the time they came from (the most major probably being the presence of a lot less gods, since many of the demigods of their time actually arose from mortal heroes of the time they're now in themselves). They have the opportunity to make some fairly dramatic changes to the world now, and I have no doubt that they will do so if they can agree on what to do. It should be interesting to watch and play along with, in any case.