Why, though? What's wrong with the old bus terminal? I mean, apart from the Dubious Fluids that drip down on you from Pipelines Unknown, which is a problem that could be solved with a renovation, an approach which is cheaper, much less disruptive, and more environmentally friendly. There wasn't a problem with it until they started the construction works for the Crosstown, and it will be fine again when the SSE ends.
The upper level I suspect will suffer a similar fate as the old terminal at Wilson - it will be used as a storage space for Crap And Stuff. It could've also been a great place to store the SRT cars they or may not actually be saving, but I think that ship has sailed.