Oceania and South America still least pecentage of representation of their well known species. Africa has more missing species, but it also has excellent representation. Asia's not too far behind. But honestly between Asia and Africa, outside of two habitat animals I'd be okay with Africa not being revisited, whereas there's a larger list from Asia I personally want to see.
Taking aside the capybara, which is the missing animal for most people at this point, I'd rather see Oceania revisited before South America. But if we took actual number of animals, I'd have a larger list of South American animals I'd want to see than Oceania. It's just that Oceania is poorly represented, that even if I could only come up with 7-10 animals total I'd like to see, the need is overall more pressing for me.
So for me it's: Oceania, South America - high priority, Asia, Africa, - medium priority - Europe, North America - low priority