I assume that expansions fall within DLC. I think that smaller expansions like they did for Fallout worked for Fallout, but I don't think it would work for Elder Scrolls. Different gameplay, different world, different content.
I assume we'll have little packets of DLC like the usual fortress/short questlines stuff but it's hard to speculate on those. I think we are just discussing the big stuff here.
My guesses, released in this order:
-Mini downloads for seeing your own cleavage, horse rabies, swords of stinking breath, etc.
-Small packs: Mage's Tower, Warrior's Cave, Assassin's Lighthouse, etc...
-Shorter Questlines: Reforming the Blades, Campaign to Become King of Skyrim, Claiming the Throne in the Imperial City as Dragonborn
-Big Expansion:
Roscrea - The Akaviri plan to invade Tamriel, and they have seized Roscrea. Roscrea's lack of protection from the Empire leads them to submit and allow Akavir to use Roscrea as a staging ground for their invasion in exchange for protection. As the Dragonborn, King of Skyrim, you go on a dangerous mission with a few close allies and a few of the only Blades in a mission that goes above politics, factions, and allegiance to the Empire. No matter what side you are on, you must cooperate with the only ones aware of the Akavir plot in order to protect your homeland. You must ferment opposition in Roscrea, gather a resistance, and dismantle Akavir's invasion before it can begin.
-Sequel:
The Elder Scrolls VI: Akavir - Take it to those Akavir fools.