No, I don't.
DLC is extending an existing game's, which is not the same as a sequel which should extend the whole game experience. A perfect example is LBP. There has been shedloads of DLC content, none of which precludes releasing LBP2 which is a far bigger, better game. If a sequel to a game is nothing more than the origianl game engine with some new content, releasing it as DLC instead of as a full-clown disk release means a cheaper option for developres and buyers, plus the opportunity to roll out incremental content instead of fans of the game having to wait a year or more for a content pack disguised as a new game. If the developers want a real sequel that'll sell to existing franchise owners, they'll actually create an improved game experience that offers something DLC doesn't.
In the end, it's a win-win, giving developers and buyers more options. As long as the developers don't underprice the DLC, they're no more likely to lose money on than on a disc release.