User blog comment:FairyRaven/Fairy Tail Chapter 400: Wings of Hope, Review and Commentary/@comment-24277053-20140913120858/@comment-7418318-20140913123420

From Zirconis we know that a Dragon's soul or ghost can be called for up to 400 years.

So even if Igneel dies, Milkyway would give him the opportinity to have a long post-mortem talk with his son.