Anyways for a future expansion, I'd say both are possible, although Jinyu would be considerably more workable. The Jinyu already have a culture with established ties to the Alliance, and while we'd probably have to add in a new tribe to truly make them playable, most of the groundwork is done.
The Saurok on the other hand have the problem of being uncivilized barbarians of only nominal intelligence. We'd need to create a tribe that is very different from the ones we've encountered so far on Pandaria. They can still be pretty warlike, but it needs to be possible for whatever faction they join to reason with them. It's not impossible (we got playable Worgen after all), but it does mean we won't get your typical Saurok.