The Oam Au guy mentioned Ganon, but weirdly he also mentioned the Goddess Hylia. May be posible, that is also Demise's real name. Since inthe original Jap version, he is never referred by that name, instead as the Harbinger of Apocalypse, and similar names.
To the other guy: The Master Sword is there, Demise or Ganon being there isn't exactly a spoiler, it is a obvious, it was now just playing the waiting game for ocnfirmation.
Something interesting to note. this may or may not be the same Ganon we know. Since Ganon is pretty much the name given to the Demon King. Seeing the mention of Hylia it is very possible this could be Demise, since in the original Jap version he was known as the Harbringer of the Apocalypse and similar names, but the case is, that we never knew his real name. So it is possible, this could be Demise, specially with the mention of the "true's hero spirit".
It seems Hyrule history is going to get very interesting with Breath of the Wild!!! It may even change all we know of Hyrule history up till now. Spoiler tags even though it is obvious what should be underneath :v