They ARE moving but I assume they want to get the GO ones used to their new home before adding other companies to the mix. I do not think there are, to date, any firm plans for the Coach Terminal site but it is clearly in line for 'something'.
I would think that rent is the main issue right now. Obviously the bus companies would be paying to use the facility, and they'll be paying more cause it's a better facility. How much more is the question.