Kerry strongly hinted at it during the Rolling Stone interview. And Riotfest is where KK will be playing already? If so that makes sense, especially if Gary is going to be there with Exodus.
I'm guessing it will be Kerry's new Band with Tom as a singer. My first thought was it might be just Kerry's new band playing Slayer songs, but iirc Kerry has said that it wouldn't be Slayer without Tom's voice.
Slayer played their final show at The Forum in Inglewood, Calif. on Nov. 30, 2019, but they're officially back, and Tom Araya, Kerry King, Paul Bostaph and Gary Holt make up the lineup. Riot Fest is set to take place in Chicago, Ill. from Sept. 20 through the 22, and it will mark Slayer's return to the stage after nearly five years.