I could really see Parkway Drive being on Mayhem, not sure what stage they fit on. Are they big enough to headline a side stage?
They have yet to tour North America for their new album and don't have any dates planned for summer (from a cursory look at their facebook).
04/05 - Kataklysm, Aborted
04/08 - Carcass, Gorguts, TBDM
04/23 - Behemoth
04/24 - Nile