Fallout 3 doesn't end with The Pitt and Operation Anchorage, to no one's surprise. Bethesda is continuing full steam ahead with further development of several more DLC packages planned for the future. Broken Steel is already on the agenda, but beyond that there are promises of more coming. Bethesda has always known about the advantages of crafting expansions (as far back as Morrowind), in both keeping a game interesting and providing them additional revenue. From a player perspective, it at least means that Bethesda isn't just moving on to their next "big thing."
This news comes shortly after we heard that Fallout 3 had netted Bethesda a Game of the Year award. At $10 a pop, if their pricing remains the same, they might find audience enough to keep Fallout 3 going for years to come - not to mention that in addition to the sanctioned expansion packs Bethesda is releasing, they also have provided tools for the gaming community to craft their own.