I walk through this island all the time. I barely see traffic at all, much less traffic that is backed up, unless it's a red light. So, based on my own personal observations, and walking at different times of the day (and sometimes multiple times a day), over nearly a year, I don't see the traffic issue. Maybe with the Don Roadway now opened that may change? I dunno. But since the DR has opened, traffic has been minimal, so far.
I think Rebel events can cause traffic for sure but who knows if they will still be there in 5-10 years..
As for streetcars, I suspect the city could be waiting for housing construction to start or finish before building in the streetcar? Personally, I think the streetcar network should be set up long before construction starts. It feels like it's all a budget thing IMO.
What I'm more interested in is... anyone want to place bets if all the buildings facing the parks are going to be condos or a mix of rentals and condos?