User blog comment:FairyRaven/Fairy Tail Chapter 401: Igneel vs. Acnologia, Review and Commentary/@comment-203.215.121.136-20140922130216/@comment-11721917-20140922131813

Possible. Demons do 'possess'. (if you really believe those 'real' stories of 'possessions'. I don't.)

The question would be how he will be exorcised.

P.S. The Great Demon Lord Dragneel, anyone? :D