http://www.gamerbytes.com/2010/08/deathspank_to_continue_on_with.php
Way back in March 2009 rebounded game designer Ron Gilbert revealed that the previously episodic DeathSpank was no longer going to be episodic. A year and a half later, that may no longer be the case.
French achievement website Succes Full has found itself with a new achievement list for a game titled DeathSpank: T.O.V. The list consists entirely of new quest lines, such as learning Japanese, getting an Engineering Degree and killing Santa Claus -- all which I believe was not in the original.
The only achievement that has any resemblance to the original is "A True Hero", which uses the same icon as "Mr. Tough Guy" in the original game, and both require you to get to Level 20. As there are 12 achieveements these aren't for downloadable content, but for a full game.
It's difficult to determine what this list might entail -- perhaps the achievements are from a build before it became the one title, but a lot has changed since the quote from Rob -- he's since left Hothead Games and EA are now publishing the game for them. DeathSpank has done quite well for the group in its month of sales, so maybe the episodic plans are back on.