User blog comment:Miskos3/Fairy Tail Chapter 490: Fairy Tail Zerø, Review/@comment-75.175.98.152-20160622053122/@comment-208.63.90.127-20160623171306

This is just a hunch, but I think it might have something to do with the one magic. Lucy has mentioned that she believes that the one magic comes from love, also when Mavis experiences Natsu and Lucy's cooperation she states that it might be the secret to uncovering the one magic. So my guess is that when Natsu and Lucy confesses their feelings for each other they uncover the one magic and then bam the war ends and happily ever after. But, for the war to end Zeref most likely has to die, which will cause Natsu to die as well, so this manga might have a sad ending. ;_;