I posted a while ago asking where the future 407 connection to the 35/115 would be, and got the answer that it will be a few KM south of where the 35 and 115 split. If they did upgrade that gap between them, I could potentially see them numbering it as 407, even if it isn't tolled. That gap would need to be upgraded though, which I don't think it will be.
As for 400-series standard highways that are not numbered as such, they're often upgraded portions of a much longer route (ex: Highway 7 to Carleton Place, Highway 8 in Kitchener). I can see in a sense why this is, but at the same time I think it creates a discontinuity in people's minds. I think a solution may be to number the upgraded section something with a 400 series designation, but to run the original route as a co-signed concurrency. An example of this is Highway 115, where part of it is also signed as Highway 7, which continues eastward after 115 ends.
A potential option for Carleton Place would be to sign the 4-lane portion as Highway 415, with both 7 and 15 continuing along that route to the interchange with the 417. For Kitchener, sign the Highway 8 connector to the 401 as Highway 418, with the 7/8/85 expressway section being numbered Highway 408. Once the Highway 7 bypass between Kitchener and Guelph is built, that and the Hanlon can be signed a single highway, since neither of those highways are likely to be extended east or north of their immediate future terminus points. That way, all of those highways appear as part of the 400-series network.
Another interesting fact: When built, Highway 417 was the only highway in the 400-series system that was not connected to another 400-series highway, until the completion of Highway 416 in the late 1990s.
As for 400-series standard highways that are not numbered as such, they're often upgraded portions of a much longer route (ex: Highway 7 to Carleton Place, Highway 8 in Kitchener). I can see in a sense why this is, but at the same time I think it creates a discontinuity in people's minds. I think a solution may be to number the upgraded section something with a 400 series designation, but to run the original route as a co-signed concurrency. An example of this is Highway 115, where part of it is also signed as Highway 7, which continues eastward after 115 ends.
A potential option for Carleton Place would be to sign the 4-lane portion as Highway 415, with both 7 and 15 continuing along that route to the interchange with the 417. For Kitchener, sign the Highway 8 connector to the 401 as Highway 418, with the 7/8/85 expressway section being numbered Highway 408. Once the Highway 7 bypass between Kitchener and Guelph is built, that and the Hanlon can be signed a single highway, since neither of those highways are likely to be extended east or north of their immediate future terminus points. That way, all of those highways appear as part of the 400-series network.
Another interesting fact: When built, Highway 417 was the only highway in the 400-series system that was not connected to another 400-series highway, until the completion of Highway 416 in the late 1990s.
