I am 100% sure it won't, because it was reprinted in the Monster Codex, and so is already in a world neutral RPG line book.
I'm also pretty sure the half Sleipnir half Frost Giant (Forgot their name, Svartaffurum or something like that) will be in Bestiary 5, as its kinda like Paizo's little lovebird that gets extreme attention in pictures and mentions. I will be surprised if that creature isn't in bestairy 5, but could be wrong.
Never bought that book, so didn't knew that. I don't really mind, they are cool, but not my favorites.