In a recent post on their official site, Penny Arcade's Jerry "Tycho" Holkins mentioned that one of two free DLC packs for On the Rain-Slick Precipice of Darkness 3 was in the works, but gave no release date.
Also worth mentioning is the imminent development of a fourth Precipice of Darkness game, also developed by Zeboyd. Tycho mentions the indie developer's involvement:
"We don't know when, exactly, but apparently there's some kind of big convention or something next month; maybe we'll try and put it out then. Zeboyd is coming up tomorrow to work on Rain-Slick 4 and the last DLC (also free) for the current one that details the fate of the player character from the first two games."
The team is hoping to get the first DLC out in time for PAX Prime next month.