First I'll repost the poem:
"Ne'er till land consumes sun can sea bear moons,
Heavens spew crimson flame, hells seem black dooms.
Stray seeds quicken in ash's grey embrace
Valiant blades forged under the Twelve's good grace."
I wrote this on my lodestone blog on January 21st:
Revisiting the New Year's Riddle
After seeing this hint in the Letter from the Producer I:
"To have players take part in engaging quests that place them in a struggle against an impending crisis that threatens their world. To have those players combine their strength and fight alongside one another. I still can't help but wonder what that ominous four-line poem might portend for Eorzea in the coming year..."
I rewrote the riddle as I interpreted it:
"Not until the sun sets in the West can the moon rise in the East
Once the enemy's airships lay siege from air and demonic foes by land.
Memories of battles lost reemerge from the Age of Calm,
As warriors stand to fight on the side of the Good."
Since the only place where the sun can be seen as being "consumed" by the land is in the East from Gridania's vantage point -- my guess is that the Garlean empire first invades Eorzea from there, especially considering The Black Shroud being the only region I know of to have quests mentioning the empire. The lore mentions that the Garlean Empire's airships can block out the sun for days at a time with their oily smoke perhaps hinting that the quests/event/instance/whatever this refers to would be in the darkness with a similar look to Dynamis. In other words, never can the moon be seen being born from the sea until we see the sun set on the horizon because both the sun and moon are hidden behind the smoke.
The second line could be alluding to their arrival in airships raining "crimson flame" from the sky (lore mentioned they had flame-throwers) and attack on the ground with their demonic-looking, metal-clad soldiers (think FFXII judges)... perhaps the summoning of actual demons as well since Beastmen tribes can summon primals. And finally, the "stray seeds" planted as a result of the indignity of occupation and destruction of Ala Mhigo lead to the adventurers of Eorzea combining their strengths to combat this threat to the world regardless of loyalties to city-states, tribes and deities.
We already knew the Garlean invasion was eminent but the initial way of looking at the riddle (ie thinking he was hinting when the next update would be based on some numbering scheme) doesn't really seem to be what the riddle was meant to tell. And they've already told us with the producer's letter a very rough update timeline for the coming months.
What I gather from the riddle is that they're telling us what kind of content is to come and maybe because of the poor launch they'll release it "in the coming year." Since they plan on intertwining the new content/quests around the game's story, the riddle could be hinting towards a quest line leading up to the unlocking of some kind of end-game Dynamis-esque invasion of Gridania (or another North-Eastern region) with implementation of the actual raid months after the release of the quest line. Hopefully the quests will be complicated enough to involve complex teamwork that maneuvering through them will take enough time for them to actually setup the instance. I doubt any kind of end-game raid in February but perhaps at least the start of a quest-line leading up to one?
Still seems like the best guess to me is the poem was foretelling a Eorzea-wide event, ie Garlean Empire's invasion, that will open up endgame content.