User blog comment:B214/Volume 22 spoilers/@comment-9595671-20160814045836/@comment-1359322-20160814060554

If 666 is unsealed during the last arc then there won't be any 30 years from now. They won't have time to do research for weapons improvement like the Holy Swords or Artificial Longinus. Remember the Isolation Barrier is like a one time thing only, they can't create another one to seal Trihexa again. So either way, 666 won't be a factor anymore just accept it.