User blog comment:Master Sima Yi/Assassinews 05-08-'14 – Assassin's Creed: Rogue announced/@comment-3446336-20140805220942/@comment-27202257-20140808044914

I don't feel like that's an outright retcon. Eagle Vision was a skill possessed by descendents of the First Civilization, it's just been spread out by millennia to all of humanity. The skill comes naturally to people with particularly high concentrations of First Civilization genes, and those with less have to try harder.