The latest rumors say that a new Metalocalypse album will be out Fall 2009 and then shortly after a the third season will start up on Adult Swim. The last half of season 2 was killer, so hopefully the third will be more of the same metal hilarity.
UPDATE: Here is what was posted in the comments section thanks to Holkie!
No rumor. As per Adult Swim:
Dethalbum II will be out Sept. 8th.
Season 3 will begin in November.
2nd tour will possibily be in October.
Dark Horse Comics will be releasing a one-shot comic, The Goon Vs Dethklok on July 22nd with a Metalocalypse comic "later 2009".
UPDATE #2 Track listing revealed:
02. The Gears
03. Burn the Earth
04. Laser Canon Deth Sentence
05. Black Fire Upon Us
06. Deth Support
07. The Cyborg Slayers
08. I Tamper with the Evidence at the Murder Site of Odin
09. Murmaider II: The Water God
10. Comet Song