User blog comment:Miskos3/Fairy Tail Episode 264: Tartaros arc: Drops of Fire, Review/@comment-24536822-20151219094419/@comment-7418318-20151219101458

There was (somewhat inconclusive) news about the spinn-off manga "Fairy Tail: Zero" being animated, which shows the backstory of Mavis and the founding of the guild.

Most of us think that the anime will show this as part of the main series instead of filler material or a break. But nobody seems to know for sure at this point (as far as I know).