The deadline for National Olympic Committee's (NOC's) to submit applicant cities will be in the Summer of 2015. The deadline to confirm submitted cities is in the fall of 2015. Public support should be stirred up after Toronto hosts the 2015 Pan Am Games. I wouldn't worry about that. Torontonians were polled if they would have supported a Toronto 2020 Olympic bid and it was in the high 80's. This was of course after the deadline for 2020 had passed.
I'm guessing Toronto doesn't want to be the first official city to declare its candidacy. Scope out the competition first, assess how winnable this could be, and coordinate it around the 2015 Pan Ams.
In other news, it was announced today that South Africa, touted as a major contender for 2024, will be focusing on a 2022 Commonwealth Games instead of the Olympics.
Rome announced it will not bid as well.