I think it depends on the rate that you booked at ... I'm sure someone else will know more but I can tell you that when I went in May they offered to upgrade my standard view room to a savanah view for an extra $60/night.
Request "best view possible" on your reservation and wait and see what happens, there are way more savanna view & pool view rooms than there are standard view... you may luck out with a free upgrade.
If it doesn't happen... check out your room first - you might be pleasantly surprised and love you location and not mind your view. There are many areas to view the animals from the hotel without having a savanna view room.
If you hate your room - call or go to the front desk to see where they can move you.. I have heard anything from free to 75.00 to switch room types.
And of course I guess the best advice would be (if you can) just book it and pay for it - if it's really important to you...