Some points are not worth debating. We know GO is going with electric locos hauling shorter trains for RER (OnCorr). It is going to be a pretty big electric loco order, so that is exciting. We also know GO is ordering more diesel locomotives in the near term, with a supplier TBD.
An opportunity for an early start for EMUs is on the Milton Line IF the solution for that corridor ends up being building dedicated passenger tracks beside the CP ones, so wires can be strung up and it can operate in a unique environment from freight. That corridor would see massive ridership with OnCorr-style frequencies, and could justify some of the EMU infrastructure like specific yards. Lots of “ifs” however.