This building, plus the precedent being set by Five and 501 Yonge are going to be adding tremendous densities to the area. Yonge (and a lot of the core) has not seen a reshaping his thorough since the 1970's. This boom might be short on big-ticket imaginative items as that one was, but it's changing the city, fast.
I think a precinct plan, as you guys mentioned, would be a good idea - with a comprehensive review of Yonge from Bloor down to Lakeshore. A thorough look at the entire stretch - as is now being done for John Street - would be in order - with all the options presented there presented for Yonge.
I think that that area in question is really from Church to University, and Dundas to Bloor. South of Dundas, it's really just the north end of the Financial District. This area has already seen tremendous growth, but realistically its potential buildout is only halfway there, if that.
Just by my count from Google Earth, there are 9 large empty lots (vacant lots or parking lots) that could be potentially redeveloped just in that small area. That's not even beginning to count the slew of low-rise buildings that exist in that area. A Secondary Plan for this area would really go a long way in shaping the development of the area.