There are 30,000+ homes being built in a new town (Seaton) north of Pickering which is immediately east of Toronto. Yes, that's not a typo -- 30,000+ new homes.   It's been in the works for a decade and those homes are being built.  I'm not why that number is not mentioned or included in the article or research. They are being pre-sold by the builders as demand is very high of course, but this will definitely increase supply significantly in the GTA.

https://www.thestar.com/news/gta/2014/01/11/pickerings_huge_seaton_development_clears_final_hurdle.html