I hope it is.
That's not to say I hope it is the last game set in the same universe. I hope they continue making games in the same world but with a different major storyline not related to the Elder Scrolls.
You can't have a game set in the TES universe that isn't tied to The Elder Scrolls because the universe
is the Scrolls. By writing on the Elder Scrolls, you can change the nature of the world.
So, if it's in the world, it's in The Elder Scrolls. Each chapter is part of an ongoing storyline, though... I'm liking how they're tying Skyrim to the past games.
The significant element of Arena wasn't the Imperial Simulacrum: It was the destruction and disappearance of the Staff of Chaos.
The significant element of Daggerfall(Taking care of Hammerfell and High Rock) was the release of Numidium.
The significant element of Morrowind, what made it a Chapter in the Elder Scrolls wasn't the defeat of Dagoth Ur. It was the destruction of the Heart of Lorkan
The significant element of Oblivion was the fullfilment of the pact between Empress Alyssia and Akatoshl/Alduin.
Skyrim... we'll have to see.
I predict TES VI will be Elsweyr, and will involve the moons.