It should get some clear foreshadowing/indication for sure, but the whole concept was still far from done and that still makes people forget or ignore many olders scenes.
The very rough idea was possibly already going on back in Alabasta and the word Haki was mentioned the first time by Blackbeard in chapter 234 which is the arc right after Alabasta, also right where we meet Mantra users that later was revealed or retconed to CoO.
Just like Skypiea had CoO, W7/EL had the CP9 and Rokushiki getting associated with haki + the direct encounter between Shanks and Newgate with Marco specifficaly bringing up the word Haki.
TB had no major possible Haki moment, however, it was right after this arc that Luffy awakened CoC againt Duval and Motobaro then following to Sabaody and so on that started exploring a lot more of haki users.