Lol, it all sounds good but, who is paying for all this free stuff @ Ontario Place?
If the space is passive (so not including the buildings); then there is no new net cost.
The grass is being mowed now.
If additional space were naturalized, that cost would actually decline.
Modest capital improvements to the outdoor space would be immaterial in terms of operating costs (ie, building a destination children's playground or the like)
Free access to the buildings (beyond parkspace washrooms) would really be dependent on how they were programmed; as simple through space, they are free-access now, where applicable.
I imagine some spaces could again be restaurants/concessions and these would be paid, as they were always were, there is no 'Free Fries for Everyone' campaign.
Concerts being free on a sustained basis is unlikely; free concerts for Canada Day or the like have existed before as sponsored events.
*****
FWIW, I really want to see much of what Ontario Place was put back, simply updated for the times.
Children's Village, A waterpark, restos, boating on calm waters etc.
Rides/Waterpark/Movies/Restos would be paid activities, but general access to the grounds, and/or passive recreation would be free.