Interesting development today; as part of a larger new funding deal between the Province of Ontario and City of Toronto, the Gardiner Expressway and Don Valley Parkway will be uploaded to the province,
https://toronto.ctvnews.ca/here-are-the-highlights-of-the-new-funding-deal-between-the-province-and-the-city-of-toronto-1.6662719. Sources are also indicating a similar deal with the City of Ottawa might be forthcoming and include uploading Regional Road 174 (former Highway 17) back to the province, although that deal has not been announced,
https://ottawa.ctvnews.ca/deal-between-ottawa-and-province-similar-to-toronto-likely-coming-sources-1.6662824.
It would be interesting to see what will happen with the announced deal with Toronto and the rumored deal with Ottawa in terms of highway designations. I'm guessing that if the 400-series highways were extended, DVP would become part of Highway 404 while the Gardiner Expressway would have some sort of association with Queen Elizabeth Way and/or unsigned Highway 451 - exit numbers for both (formerly) municipal expressways are already continuous with the respective 400-series highways.
As for the possible uploading of RR 174, it would be interesting to see how extensive that would be and what (if any) number would be used. For example, would an uploaded RR 174 only include the freeway section near Hwy 417, the entire section within Ottawa, or the entire former Hwy 17 section that includes Prescott and Russell County Road 17? Also, would an uploaded highway retain its Hwy 174 number, revert back to being Hwy 17 (pre-1998), or maybe be renumbered entirely? The local Liberal MPP introduced a bill to upload the entire route in 2021,
https://ottawa.ctvnews.ca/mpp-calls-on-ontario-to-take-over-responsibility-of-hwy-174-in-ottawa-s-east-end-1.5641034, but at this point it is still remains downloaded.