So, about the new theme, "Dragonsong"...

[Enkidoh]

Although the true meaning behind it only Ferne can answer (given the fact he co-wrote the lyrics for it), so take anything I say with a grain of salt, but personally I disagree it's about Iceheart (although it's clear in the video she will play a major role in the 3.0 story). Instead, I believe the song is actually Hydaelyn lamenting the turn of events with the

fact the Warrior of Light (Her chosen) lost Her Blessing due to Midgardsormr's meddling, their resulting fall from grace due to the assassination of Nanamo and being framed for the crime, and Raubahn's despair over losing her, leaving Ul'dah without a legal ruler (as Nanamo was the last of her royal line), with the end result of the Eorzean Alliance bickering among themselves distracting them from the true evil, that is, the Ascians and their ongoing quest to rebirth Zodiark, which threatens Hydaelyn and everyone who dwells on the planet.

Additionally, the words also at the same time align with the central theme of Heavensward, the Dragonsong War and the resentment both sides in the conflict have towards each other, regardless of each other taking the moral high ground.

But as I said only Ferne knows the true meaning behind it so until he pops in on the Lore forum with information about it take my guesses and assumptions as just my own opinion which may not necessarily be correct.