I agree with your points here. I’d add that Highway 6 is pretty much free flowing inbetween where the Morriston bypass starts and Highway 5/Dundas, so there isn’t much need after those are dealt with.I am doubtful we will see a full expressway on HWY 6 anytime soon, but I’m of the opinion that it is gradually moving in that direction. I don’t think it will be justified until both KWCG and Hamilton are larger, until HWY 7 is complete, and until HWY 6 is full grade separated through Guelph. I wouldn’t be surprised to see more control on access and intersection removals, as well as property acquisitions/expropriations along the highway in the near future, though.
As for HWY 424, I don’t think that is going to have much of an impact on HWY 6’s future, as HWY 6 is a much more direct connection between KWCG and Hamilton. I think that HWY 424 is going to sit on the back burner until Brantford fills up it’s northern expansion lands (which probably won’t take long given the crazy rate of development out there), and Cambridge development jumps to the south side of McQueen Shaver Boulevard, which I am now suspecting is going to end up forming part of HWY 424 in the future, given that a 60 m ROW is being maintained along that corridor.
I initially brought up the 413 because I can foresee people using Highway 6 to get to the 401 to bypass Toronto via the 413, rather than using the 403 and being forced to grab the 407. Network effect and such. There is a small but growing number of people that take highway 6 at rush hour off the 401 to avoid the QEW (particularly if your destination is north of the 401, where under typical rush hour conditions travel times vs. QEW are negligible)