Back in 2010 there was a really interesting sports/community complex proposal for the RL Hearn, see
http://news.nationalpost.com/2010/06/22/sports-complex-plan-unveiled-for-mothballed-hearn-station/ It was an innovative energy saving design (an ironic angle on converting a coal-fired power station for other uses!), the design/engineering team were very experienced in this kind of public project: Behnisch Architekten
http://behnisch.com/projects/426 TransSolar Climate Engineering
http://www.transsolar.com/ and ERA Architects
http://era.on.ca The Goethe Institute sponsored a public presentation of the proposal at the MaRS auditorium
https://vimeo.com/12854835 (the Hearn proposal starts at 29:30 on this video).
Among the problems with *any* proposals for the Hearn's reuse are that it has been privately leased for 30 years to a private corporation that seems not have the financial muscle to organize funding for any commercial project--the place is just so massive--and that this situation of the private lease means that public institutions really have no leverage or influence on what can be done with it, e.g. the City issued a demolition permit for the complex at one point and it has stated that there is no way Hearn can receive a Heritage designation because of the leasing arrangement. Meanwhile, the lessee has been removing all the "non-structural" steel from inside the building (lease costs have to be paid somehow!), renting it for post-apocalyptic film-shoots, and I believe the only maintenance being done is what is necessary to secure the place against the increasing hordes of people wanting to photograph post-capitalist industrial ruin-scapes.
If the Port Lands ever get the kind of mixed residential/commercial neighbourhoods that Waterfront Toronto has been planning for years, then I think the Hearn could be an interesting conversion project for a mixed commercial/sports/community centre serving that whole area; if there was some kind of LRT access to it, Hearn could end up serving a lot of the urban core of Toronto as a sports centre. (E.g. maybe the non-revenue access rail tracks to the new Leslie Street TTC storage/maintenance barns could have gone somewhere near the northern part of the Port Lands to join up to the regular tracks, and those access tracks could have become part of a later regular track network serving the Hearn and Port Lands area).
But in Toronto we lack public-spirited ambition, our "vision" is hobbled by not wanting to pay for things, or paying for things that we don't really want or need, but that satisfy a particular conjunction of political circumstances.