I've already ended 5e for a campaign I recently started. In the last one, the players thwarted an effort to change Eberron's cosmogony by linking it a to a whole different set of planes than the usual ones. They, wisely, restored the original ones, based on a Giant device used to unlink Dal Quor. They ended at level 17... it was great. They were very happy of saving the world. In the recap, though, I reminded them that while they, indeed, had talked a few things about the necessity to take care of breaking the link to Xoriat... they had absolutely forgotten about it in the last 5 sessions and, indeed, linked it in the state the giants had left the device. So, Plane of Madness it is.
So the current campaign occurs a few years later, in a world changed in subtle way by the link to the Realm of Madness. Great works of arts have been created, but also a few problem sprang. The world isn't really the same. Which we reflected by switching to Mythras rules (porting the dragonmark powers to it) as a group of dragonmarked heroes assemble to... fix that strange feeling of off-ness they have deep inside them.
It is possible it will last far after 2024, so maybe I won't run 5e ever again, just playing in it.
