Building subways just because the people think they are too good for LRT hardly strikes me as being a wise use of public funds. Transit planning should be done with care to the existing and projected population density, building the highest order transit everyone is extremely fiscally unwise. And since it's not a new line, but an extension of a pre-existing one, that means you'd have to run the large sized TTC stock deep into suburbia. And that can look one of several ways:
a) to avoid wasting money, don't run every train into suburbia - and now you have an unattractive frequency. Why would you wait 10, 15 minutes for a subway train for a local journey when you can drive in much less time?
b) to avoid wasting money, you run trains of various lengths, which would be an operational nightmare and shorter trains would probably not be sufficient in the denser parts of the line closer to Yonge Street
c) to avoid operational complexity or unattractive frequencies, you run the full service into suburbia, which would be a waste of money
And because the experience with subway expansion so far is that they insist on running it underground to pander to the NIMBYs, that means the price tag would be astronomical for that, too.
If the suburbs want subways, they should pay for it themselves entirely out of their own pockets. Why must the entire rest of the province fund expensive subway projects to sprawling suburbs just because the people living there think they are too good for LRTs? How many new GO bus lines, new tracks or corridors for the GO train, new LRTs or BRTs can the billions these subway projects cost buy us? The worst thing about the Fords' legacy is that it has empowered every suburbanite to demand the biggest, most grandiose projects to run through their neighbourhoods, all on someone else's dime.