DLC and Expansion packs are so not the same thing. That said, I can only hope that TES V (assuming there is a TES V, of course) will steer away from 'DLC' and back towards the 'expansion pack.'
I agree fully, expansion packs are large addons to the game that add a considerable amount of content and may also introduce new gameplay mechanics, they are also distributed in the same fashion as the full game (For example, you can buy expansion packs in stores.) DLC is a cheap attempt to milk a game for more money by selling players small plugins that are often no better than free, player made mods, they're also usually overpriced, also, as their name implies, they are downloaded. Maybe if the downloadable content is decent, I might consider getting a combined package of it in stores if such a thing is made, but otherwise, I can do without. Other than that, back before the obsession with downloadable content, you'd never see them market something that lets you put armor on your easily replaceable horse as an expansion, because no one would want to buy such a thing for the same price as they'd pay for an entirely new landmass, complete with dungeons, quests, and lots of new loot and enemies.
What I want Bethesda to focus on is proper expansions, like Tribunal and Bloodmoon for Morrowind, or Shivering Isles for Oblivion.
If Bethesda's resources are focused on downloadable content, that may mean that we won't get proper expansions, look at Oblivion, Morrowind had two expansions, whereas Oblivion only had one, and Fallout 3 had none (Okay, Point Lookout has some elements of an expansion since it adds an entirely new area you can explore freely, complete with both a main quest and side quests, but I don't think it really had enough content to qualify as a new expansion.)