I think Sydney have mostly met expectations. I wasn't sure how a city zoo could be built from scratch and hold some of the most popular and well known species, yet Sydney has extraordinarily found a way to do this.
Sydney Zoo is only 40 acres in total, a little smaller than Melbourne Zoo. For a zoo that wants to obtain more species into the future, especially large ones; i'd love to see an expansion. There's the space if required.
Honestly, considering Taronga already has elephants, i'd like to see Sydney Zoo maybe get into Hippos instead into the future. This gives them another drawcard against Taronga; the only other main ones being baboons and orangutans.