It's open and apparently they may limit the number of visitors. But for those of us who ride in from elsewhere, I don't know how that will work.
https://trca.ca/about/covid-19-related-closures/
Oh it's definitely open. Maybe it'll be like Halton. Apparently for the Halton Region Con. Areas you have to book a spot/time slot in advance and the gate will only open if your license plate matches your pre-booked/paid reservation.
I have friends who have been making those reservations and apparently, the system is working well.