I wonder if York University would be considered a fourth "zone" considering the substantial new investments in the area, such as the Canadian Tennis Centre, the York Pan Am Athletics Stadium, and the York subway line which *sigh* will hopefully be complete by 2024.
As well, there are a number of new Pan Am sites that could be used for the 2024 games, many of which are outside of the three proposed 2008 "zones." These include the Scarborough Aquatics Centre, the renovated Varsity Stadium, the Caledon Equestrian Park, Hamilton's Tim Horton's Field, Milton's National Cycling Centre and Markham's Pan Am Centre.