The plan itself is actually reasonably good-- Canadian cities have a better record of re-gentrification than their American counterparts. Regent Park was Canada's first (I think) attempt at public housing, and it's layout (Hard for effective police and fire access in many spots), age, and lack of space to facilitate mixed income living let it acquire a certain amount of 'ghetto synergy'.
Advantages compound and so do disadvantages.
Canadian cities like Toronto, Montreal, and Vancouver have done very well by re-gentrification. Mostly because the post WWII American hype about the burbs never permeated resonated here as much. (Not to say that we lack burbs.) There are tremendous social and economic advantages to having a healthy level re-gentrification that basically start compounding from the day a person is born.
It makes a tremendous amount of sense to correct historic oversights like Regent Park. (And to finally get a subway line out to Jane and Finch, etc...) The best thing you can do from both an economic and social perspective is encourage mixed income turnover with a healthy level of re-gentrification in all neighbourhoods, and to build dense human livable neighbourhoods in the first place. Which is not to say that the area won't remain 'bad', but it will be 'lass bad', and not 'bad' in the American / Developing World sense.
It's nice to say, "Oh well, the residents will just shit it up!", but there are severe long term consequences (For Conservatives: think expensive.) if you allow a ghetto to maintain its 'synergy' over the long haul. About the only problem with re-gentrification is that it keeps property values and rents higher, but that is offset by vastly higher productivity in the formal (and taxable) economy, reduced crime, etc.
More problematic are 'the burbs' which are under-taxed, over-served, car centric, low density, and filled with far too many people who bitch about their taxes without realizing that they're the real parasites. (That's a dirty non-secret-- the numbers on that have been there forever.)
TL;DR: Policy makers must take a firm hand and encourage re-gentrification, and to discourage sprawl or things 'go to shit'.