If the Conservatives are smart, they will put all future GTHA transit money in the next few years towards turbocharging GO's development. For example, advancing plans for electrification. That's the biggest bang for the buck. On both transit and votes.
If it hasn't been politically sexy for the Provincial Liberals, I doubt it would be sexy for the Federal Conservatives. From what I've seen, politicians like projects that can benefit toss-up ridings. This usually means local transit.
But yes, it would be nice if some politicians recognized the value in a GO REX implementation.