Everything up to this point regarding the Legendary Fyr’alath has been encrypted, but it seems that the first piece of datamined information may hint at one of the quest steps.
Fyr’alath Questline Hints
Blizzard has done a good job with encrypting anything related to the upcoming Legendary 2-Handed Axe Fyr’alath. However, it seems that one thing might have slipped through, highlighting a portion of the questline needed to acquire Fyr’alath!