You've already been assured that you'll never run out of slayable dragons in Skyrim. In an interview with Wired, director Todd Howard revealed that the game features an inexhaustible supply of quest content, as well.
Using the "Radiant" quest system, the game randomly generates missions for each of the in-game guilds, as well as tasks offered by other NPCs. Examples cited by Wired include collecting flowers for an alchemist or hunting for bandits.
This likely comes as bittersweet news for people who have experienced Bethesda games in the past. Sure, you'll never run out of content, but how long before you have to defeat a monster who's embedded in a tree, or go on a quest for the dagger of ^^^^^^ARTIFACTNAME?