User blog comment:IamJakuhoRaikoben/Chapter 398: The Final Duels, Review./@comment-25111584-20140903065859/@comment-5303512-20140903133849

My guess is Natsu will lose Igneel if E.N.D. Returns and is stronger than before.

For Erza it has to be either Jellal, Milliana, Kagura or Minerva.