I think bands like The Chemical Brothers and Kings Of Leon are just not able anymore to sell enough tickets to headline PKP/RW. Lokerse Feesten is a festival with only 10k capacity! In addition, this show is actually a replacement of their Sportpaleis show, which sold horribly bad.
Your 4 main contenders to headline this still dont have a show in July/August in Belgium (AM, Dua Lipa, F+TM and Editors). Dont think there will be any crossover in headliners with RW.