Talked to a promoter tonight who told me he was offered two different tour packages in his area that were for Mayhem Fest off dates. Bands he talked about (he fished some info for me) along with those that were offered included Rob Zombie, Deftones, 5FDP, In This Moment, Amon Amarth, Behemoth, Job For A Cowboy and Battlecross.
No mention of KsE, MIW, Chelsea Grin or Emmure, etc. That doesn't mean they aren't playing, their names simply were not mentioned. He did say he was told that they are still finalizing a few bands for Mayhem Fest and that the line up is not complete barring a few smaller bands (my guess is the Sumerian Stage and maybe a few more). Those bands listed above came from two sources who work in the business who are fortunate enough to relay some info to me.
1-13 Philip H. Anselmo & The Illegals