This is interesting, however we know little about Termina and wether or not the Kokiri exist there. In addition, some other species such as the Garo don't have a Hyrulean counterpart so its likely the monkeys are just talking animals. However it is quite interesting and a possibility the monkeys are The equivalents of the Kokiri.
No, I don't think so. If Termina is a parallel world to Hyrule, they might be replacements for the kokori in the forest, but the kokri didn't become monkeys.
We know from Wind Waker what they became (koroks).