It hasn't been applied to that route since last century, with the missing piece through Cambridge, and not running south of Dundas Street. Nor does either make much sense, with better roads down 5/6 in Hamilton, and up the old 24 and 401 in Cambridge. But if they ever uncancel expressway around the western side of Cambridge, then I suppose that could be 8 or 408 as well.I'd be inclined to maintain 8 as a through route from Dundas to Goderich, with 408 applied as appropriate, with the Kitchener - Guelph and any southern extensions numbered as 406 with a new number applied to the 406 in Niagara if one didn't want to cosign sections of the QEW.
Personally, I think the Conestoga should be a single route number for it's entire length. The current arrangement where it starts out as Regional Road 85, then turns into Ontario Highway 85, Ontariio Highway 7, and finally Ontario Highway 7/8 is unnecessary.It's as bad as the 7, 7/115, 115, 35/115 mess. (or even the 7, 7A itself from Peterborough to the GTA ... does anyone in Peterborough ever actually follow the 7 alignment southwest of Peterborough to get to Lindsay, or follow 7 or 7A through Port Perry to get to old Highway 7 through Brooklin (or the 407).