That's a very interesting question, indeed. As far as I understand, Volbeat are the biggest of the expected names so far? I don't think that they can carry that Thursday on their own - at least not with a lengthy tour just months before the festival. They would either need a strong co-headliner or stronger undercard to sell out that day.
Do we have any
realistic ideas about other bands that could be Thursday's main headliner? BMTH (could go to Werchter) or Sabaton don't seem to be as big as Volbeat. Others like MCR, Slayer, SOAD etc remain quite unlikely.
I'm really curious to see what they might be cooking up in

Je pense que BMTH est plus grand que Volbeat... absolument !