It's also slated for removal (at least the upper viaduct), a very large park is meant to be built in its place (the architects that designed the High Line park in NYC were going to be designing the project, at least as of 3 years ago).
There's only so much money that (is politically viable) to spend on this stuff at any given moment. As soon as the line to Langley is done we're gonna see a pivot to building out to UBC or North Shore.