A portion of a PLAY interview with producer Atsushi Inaba..

P: Do you hope games like Madworld can promote more mature titles on the Wii?

AI: Well, more mature titles would mean that the users will have more games to choose from on the Wii and I think that is a good thing. It would be great if Madworld can really kick off that trend.

P: Lastly, do you view Madworld as a stand-alone title, or would you like this to be the beginning of a new series that might make it to other consoles in the future?

AI: We’d obviously love for there to be a sequel and will definitely consider making one depending on the feedback we receive from players of the game.

Full interview here

I'd buy a sequel. Provided the first one can hold my attention.

So would Dennis Dyack but that just goes to show make sure the first one is a success before talking about sequels.

hope the first one sells good...
if it deserves

He's at least confident that he's made a great game, let's leave it at that.

I agree, get the first game out before talking of a sequel but it was a prompted question. At any rate No More Heroes is getting a sequel with only 400k sales so there's certainly hope this will as well.