October for the US one from what I understand, which is the same month the 2013 Fanfests were held (where Heavensward was first announced). So there's a long time to go before we hear anything more.

Also that article mentioned nothing about Doomtrain, so I think you're making a big assumption here (the only reference ever mentioned about Doomtrain was a very vague reference made back during last year's Rising event) - as it is FFVI's Phantom Train is already mentioned in the game as being the nickname for Garlemald's (non undead/summon) railway that runs between Castrum Meridanium and Castrum Centri, so I'm wondering how the lore could add Doomtrain into the game, unless it's a newly created Primal or something... but I guess we'll see.