Jack Black and Kyle Gass said that they have booked a date at Santa Monica Pier on October 19 for the one-off event, but they have yet to sign up any acts.
Flight of the Conchords, Tim Minchin and South Park creators Matt Stone and Trey Parker were named as possible headliners.
When asked whether they might stage a Blur vs Oasis-style rivalry with Flight of the Conchords, Black told Rolling Stone: "We actually have been talking about joining forces, because we've always wanted to do a double bill.
"We're working on a festival, called 'Festival Supreme'. It'll be a meeting of the minds. It's gonna be like Mount Rockmore, where you've got your Flight of the Conchords, your Lonely Island, your Tenacious D, your Zach Galifianakis, your Spinal Tap, your Eric Idle."
He continued: "You get your Tim Minchins. You get your Neil Hamburgers. You get your Tim and Erics. You take your Mr Shows - they've got incredible songs. Get your dudes from South Park, Matt and Trey.
"October 19th. Circle that in your calendar. Now there's no guarantee who's gonna be on the bill - it might just be Tenacious D and Weird Al. But that's a long ways off.
"And the D is coming to a town near you, and you don't wanna miss the old-schoolness of me and KG, because it's boner-riffic."
Tenacious D embarked on a mini UK tour back in October in support of their latest album Rize of the Fenix.
Watch the video for Tenacious D's 'Rize of the Fenix' below: