I believe the future of expanded rail service in SWO lies with the North Line: Metrolinx owns half of it, there’s minimal freight traffic (unlike the South Line).
If rumours from current railway employees are true, CN wants to sell their portion of the Guelph Sub, and Metrolinx doesn’t have a keen interest in expanding service west of Kitchener (the London pilot project was apparently only for political reasons).
VIA has said multiple times in their reports that they would like to expand service on the North Line. As user Urban Sky says, time slots and equipment shortages pose a challenge to this. Furthermore, unless they get additional funds from the federal government, I can’t see VIA purchasing the remainder of the Guelph Sub, or paying CN to replace the bolted rail.
My pipe dream is for increased speeds on the North Line, and adding VIA trains from Windsor to Toronto via Kitchener. But I am also realistic: none of this is happening if/when funds are available, and agreements are made between CN, VIA, and Metrolinx.