It's really hard for players to feel like they have some agency over the Old World when there are characters like Nagash running rampant. Most players I know like to invent their own characters, their own little histories, and carve out their own little piece of the Old World, whether it is some Bretonnian Duke in a out of the way castle somewhere, or an Imperial general or an Orc Warlord, we all like feel like we're in control of our little 'patch'.
And that's really hard when you've got literal gods and supermen running around tearing everything up. GW will, if it know's what's good for it, restore some kind of balance to the Old World once it has finished with all this End Times stuff. I imagine that the End Times will be a complete story arc, and at the end of it we will get a 9th edition, which will represent the Old World as it exists after the End Times story arc is finished.
So how do I think this story arc will end? I think Nagash is going to curbstomp Chaos. Not the gods themselves, but he's going to beat Archaon and his buddies so hard, their ancestors are going to wince. Afterwards, he'll be in a weakened state and I think it is then that he will be taken out. He may be killed, or just reduced to a weakened state, but he won't be around killing everything anymore. And as a result, we'll have both the Chaos threat reduced to a non-critical level, and the Undead restored to their normal threat level, and enough of a mix up in the Old World that we can get some new fluff and new units in our other books. Tomb Kings will be an interesting one given that Nagash pretty much owns them now.
