Hard for me to weigh in due to perspective... It's possible I took the Thancred reveal for granted because Yda, Papalymo, Y'shtola, and Thancred were all introduced in the game's original 1.0 release in 2010.
It could be that this was an oversight on SE's part in terms of looking at the story from the perspective of someone who's only just now coming in from where A Realm Reborn starts.
Edit:
Okay nevermind... I -didn't- remember that, but it's a fair point. You do interact with Thancred quite a bit prior to the reveal. Also, in an on-going MMO, it's hard to state whether or not "nothing" was done with this; the story ain't over until they announce that they're done creating new content for FFXIV.