Certainly the building will remain standing, but the actual yard will be the most likely thing to be developed. Nothing has been made public yet, but one of the main theories is that the elephant exhibit will turn into a gorilla exhibit. (this is talked about in some news articles about the elephants leaving) It would be great, but I see issues with the relatively small space the yard, off-show areas, and W.I.L.D. Place (that stage near the elephant barn) would provide. This is especially so with the barn taking up some vital area that would infringe upon the design of whatever is built there. Plus, the barn would obviously too small for a decent indoor ape exhibit. I think Buffalo Zoo should use Lincoln Park Zoo's African ape exhibits as a model for building dynamic indoor and outdoor spaces in a relatively small footprint.
Here's an idea: what if Buffalo Zoo held chimpanzees instead of gorillas? A smaller ape means a relatively smaller footprint will be fine, they can make use of vertical space, and they'd be the only zoo in NYS to have chimps. The biggest issue I'd see here would be any restrictions placed on sight lines and the heights of buildings because Delaware Park (to which the zoo is adjacent) may have some restrictions on the heights of buildings in order to keep to a certain aesthetic, for lack of a better word.
Part of me wishes Arctic Edge could pivot 90 degrees so the elephant barn can be turned into an environmental education center and maybe there could be more space for polar bears, a reindeer exhibit, or expanding the rhino enclosure.