Given that this first Gorilla enclosure is behind the House and nowhere near the proposed new Ape developments, is the plan really to demolish it too, or might it serve a while longer as a temporary holding area e.g. for Apes during the various changes that are planned?
From memory this was the very first one. Then possibly the Orangutan one. Then the Chimp 'colony' building and the second Gorilla house(now Chimps), finally the third(current) Gorilla house. Somewhere along the line the old Elephant house was redone for the Bonobos/Gorillas also.
The four houses that would definately have to make way for the new developments are the Gorilla House, 2 Chimp Houses and Bonobo House. Whether they also intend to do away with the other remaining ones built in this style over time remains to be seen- probably is my guess.