This came up recently in the thread about the actual bank buildings, but there was a newspaper article in the past year or so on the two banks, and lack of any foreseeable developments on those two sites. Michael McClelland, one of the city's foremost heritage architects, was interviewed in the article, and he said that he'd been approached something like a dozen times over the years with various schemes to redevelop the two properties. Nobody could make the numbers work. It's not lack of interest which is keeping these two buildings dark.
If Simons wants to expand into the Toronto market, I can't imagine that they would pick such a difficult site. Even if they could figure out a way to do it financially, it would inevitably be a complicated and lengthy approvals process, which would delay their entry into the market. Never say never, but it seems unlikely.