The critter castaway and bird garden's area would be perfect for a coaster, there is not much in that area; if you enter the park and go to the left, you encounter Gwazi and (not including sesame street since this is strictly for little kids) then that is it, a long walk of no rides until you enter Stanleyville.
The Tut area I really think they ought to be a non-coaster thrill ride there, I'd really love for a topspin ride or something.
I know that technically they could have a coaster there and have it go into the Serengeti, but it would destroy the beauty of it.
Two new rides would be idea really, and then once that is done, they can finally figure out what to do with the Gwazi area, I expect the whole Gwazi area to be a major overhaul that will see the construction of a whole new land, would be nice since it is kind of a mess there.