We can only really speculate what happens to them. Since we see stain glass of them in Wind Waker we can assume that they live to tell their story.

Well, I'm guessing that old Rauru stayed locked up in the Temple of Time and that KG his owl spirit probably went away. I'm guessing that Impa went back to repair the damage in Kakariko, Darunia to reorganize all of the freed gorons, Ruto to thaw Zora's domain, Saria to help the deku tree sprout grow, Nabooru to lead the Gerudo, and Zelda to rebuild the castle on the ruins as after all the only thing left was a smoking crater.

But we don't know because of the time paradoxes and all of that confusing stuff.

And yes, they would have stayed to guard the temples and make sure peace was restored.

Well think about it..they're dead (except for Zelda. Rauru is that old, Darunia goes to fight Volvagia and isn't seen outside the chamber of sages again, Nabrooru gets blown right in front of you, Saria isn't seen outside of the chamber of sages again, Impa went to Kakariko Village and wasn't seen from again, and. Ruto is seen once and not again (probably drowned.) They probably are just spirits.

Well in Majora's mask (sequel to ocarina of time) Darunia is a ghost and his spirit goes into the goron mask that link collects so most likely they all turn into spirits.