Oh yes, the boys are coming back. Taken from their own site:

Yes the rumors are true....Tenacious D has begun recording new music for their upcoming film PICK OF DESTINY. John King is the producer behind the board and dont be surprised if there are a few special guests on the album as well. We will keep you posted on some studio reports and perhaps some pictures from the studio as well. Stay tuned! </blockquote> Get the offical D goodness & news over here.