User blog comment:IamJakuhoRaikoben/Chapter 499: Gray and Juvia, Review./@comment-4449950-20160830081738/@comment-5303512-20160831210351

Two things:

1. I don't think that just because Tenrou Island fused with the main land doesn't mean that the immortality will spread to the rest of the land, it is just the tree that gives FT mages immortality, so it's effects are limited to the range which the Tree is rooted.

2. Fairy Heart is just infinite magic power, unless Mavis learned some forbidden resurrection spell, I doubt that will do anything.