Here's a neat tool that some of you may find interesting - the
MTO Permit Controls Map database.
I had brought it up a couple of pages ago but I figured it might be useful to link it for seeing which major provincial highways could emerge in the future. If you filter by the "Grading or Landscaping" category, you can see the roads that MTO maintains landscaping permits for, at varying sizes for major (planned and existing 400-series or expressway) and minor (planned and existing four-lane non-grade separated) highways. There are a large number of minor highways that hold freeway and interchange-sized grading permit controls. It's worth noting that many of these highways will almost certainly never happen due to population densities in the areas they run through, but it's interesting to see which corridors could eventually host a major highway in the future as our province grows. There are also former controlled areas that haven't been removed from the map yet, like the cancelled St. Thomas-Aylmer expressway alignment. Additionally, the entire area of northwestern Ontario doesn't seem to have any data, so the map is certainly not up to date or maintained on a regular basis.
Some interesting new (or old but stagnant) alignments I found on there include the HWY 115 Northeast Bypass around Peterborough to just south of Lakefield, HWY 417 Northwest Extension from Renfrew to just south of Pembroke, HWY 3 between the Grand River and Port Colborne, and HWY 17 both east of Sudbury and east of North Bay. There are others on there like the Bradford Bypass, new Kitchener-Guelph HWY 7, Morriston Bypass, and HWY 404 Northeast Extension that we already know about.