Historically oracles are mortals with a special divine connection, such as the oracles in Greek mythology. Personally I think that means that while they each have a special connection to their patron goddess, they themselves are born, live, and die and then a new Oracle takes the place.
My philosophy on the timeline now is the same as Winston Churchill’s:
“It is a mistake to look too far ahead. The chain of destiny can only be grasped one Link at a time.”
I don't really mind the idea that the Goddesses took mortal forms after creating Hyrule.
Explains why the Gods are so absent and why they'd want to make a world in the first place.
They just wanted to live in the little Minecraft house they built.
Expanding upon the concept (this is actually something I have as a headcanon), when we see the creation myth, it tends to end with the goddesses clashing into each other and leaving behind the Triforce...
It's always described as "the place where the goddesses left this world", but what is related to "leaving this world"? Death. And what happens when certain god-like characters who have the Triforce die? We see Ganon dying and vanishing, leaving behind the Triforce of Power.
Sooo, perhaps not reincarnation, per se... Instead I would say Zelda except her SS incarnation is Hylia's Oracle. The oracles aren't reincarnations so much as they carry their respective deities' powers and legacy in the mortal world.
@FroyoClaus That is very interesting. I never thought to interpret "left this world" that way.
edit: Okay, part of the idea it's interesting is that I've speculated before that reincarnation, or at least a certain sort of reincarnation are limited to gods and god-like beings (Hylia, TP Ganondorf) being reincarnated in weaker mortal bodies (SS Zelda, FSA Ganondorf), so the Goddesses doing some kind of creation-suicide-reincarnation plan to live as mortals in a world of their own making would fit that same paradigm. (Of course, I don't have a lot of evidence there; it's just an interesting idea.)