Shawn Crahan says the band are still struggling with the loss of Paul Gray The metal band took time out following the death of bassist Paul Gray in 2010 and haven't released any new music since 2008's All Hope is Gone.
But speaking to Daniel P. Carter, Clown said after Download they'd probably "start writing and getting ready".
Slipknot headline Download on Friday 14 June 2013.
The Iowa band's performance will be their fourth at the festival and their second headline slot, having topped the bill in 2009.
Clown said that the band were still feeling the loss of Gray and weren't yet ready to write a new album, but that Download could be "a way of moving forward".
"I imagine after we do Download it won't be long after that I think a good portion of the band will probably be getting together to blow the dust off the future - and starting writing and getting ready.
"I don't know exactly when that's going to be, there's no plans, but I feel in my heart and soul that after Download it'll be a really good feeling and we'll all be getting together."
The eight-piece band have played some live shows recently, including their own Knotfest Festival in August 2012.
They also released a greatest hits album this summer called Antennas to Hell.
Iron Maiden and Rammstein are the other two headliners at next summer's Download Festival.