The triangle is actually similar in size and shape to the lot the Juliana Apartments sits on. Something can be built there but given the location and the road network, vehicle access is a bit awkward. A residential project seems a poor fit. More likely is some sort of smaller trophy building like the library, adding to the zone of visual appeal developing here. I sort of imagine an eventual expansion of the library, or some other public facility, connected with stunning aerial link.
A similar problem occurs with the long, irregular plot of land on the slope down from where Slater used to run. It's roughly three times as large and is really nicely situated for an attractive development. But it looks as though they've made no plan for how to use it or drive a vehicle onto it. So, just a park?