Anecdotally, there was a 1 hour wait to charge in Kingston on Monday afternoon. I only charged in Bellville and the station was not quite full then, though I think 3 stalls were out of service.This weekend I experienced full superchargers at Port Hope, Kingston, Cornwall, and Levis. The 401/20 corridor really needs some attention soon with the rate of new deliveries every year.
I don't think the addition of Brockville alone will fix Port Hope but it will certainly take the pressure off Kingston and Belleville. If there is nothing else on the map now, I wouldn't count on any more Supercharger infrastructure being built within the next 2 years. Make sure to maximize your destination charging opportunities accordingly.