In an official interview nhere
http://www.g4tv.com/videos/52434/elder-scrolls-5-skyrim-gameplay-preview/
Todd somewhere in that NON LEAKED INTERVIEW for any moderators
"We thought, maybe we should wait for the next generation of consoles, because we're going to reboot Elder Scrolls"
- Todd Howard
Also Michael Kirkbride(the person that wrote most of the morrowind books) always said something about an apocalyptic event.Some of his thoughts featured nhere.
http://www.imperial-library.info/content/forum-archives-michael-kirkbride
Now somewhere I believe in the elder scrolls 6 we will attempt to save the world only to hear word that the world will end no matter what in a few centuries. Baring similarities to the 3rd terminator where they never saved the world merely postponed it.
The greybeards were hinting that we were not saving the world merely postponing it (another terminator 3 reference).
I think a rebooting of the elder scrolls would be very nice since it gives us opportunities and possibility for even more future games.
however a reboot of the elder scrolls means both the death and rebirth of the Elder scrolls.After all the death of the old world means the birth of anew.
Mabye the Thalmor will succeed after all but will be stopped before some ritual but just got far enough that the world will inevitably end. After all it has been thousands of years since the merethic era and a new merethic era would mean a full head on fantasy rpg action game.That's one possibility.
Don't forget of an other possibility.

So the world is going to end with the coming of evangelical locust men spreading their new religion to all of Tamriel(As said by Michael Kirkbride). Probably a bit much for a DLC, Thalmor war seems a lot more likely. But given the history of expansions (Bloodmoon, Tribunal, Shivering Isles) it’s probably going to be a totally separate story, not something as connected to the main story as the Thalmor vs. Empire.

Just hypothesizing here, but when you killed Alduin you sped up whatever metaphysical immanence He is describing in the above text. Alduin's soul or essence, or whatever, is the only one you don't absorb in the game; it escapes to... somewhere. And if we assume it did legitimately die and is no longer in possession of that energy you have potentially released everything he's eaten since the dawn of time. I'm not sure how the mechanics of it all work, but you could have released countless races or intelligences back into the universe when you did that.

They could continue with the Thalmor/Empire dispute, while having everything go bat[censored] in the mix, as ancient forces awaken and start doing inexplicable things.

All of this could mean something but could mean nothing.I think the best thing would be a reset of the elder scrolls with elder scrolls 6 being the last throws of the current world.

So the world is going to end with the coming of evangelical locust men spreading their new religion to all of Tamriel
-Michael Kikbride

This could all mean nothing but mabey we are in the last throws of this world.
So go on hypothesize.
And remember the locustmen are always watching us and waiting.