Slim to none for the following reasons:
Local stadiums are all too small and no government entity would pony up the money for a new park right now. Apparently this is now a political football...ahem...even in a place like Los Angeles, so no way a ruling party would want the backlash over funding the NFL here. Groups like "Bread not Circuses" have already flexed their muscles by killing Olympic dreams around these parts, and they would step up to knock the NFL back south.
Second, the exchange rate is too fluid. Right now the team would be decent as the exchange is high, but exporters want that number to drop again...and we are a nation of exports, so the 65 cent dollar is good for that business, but not good to keep our sports on equal footing.
Third, Toronto is no longer the financial driving force that it once was. For a league that is usually looking into the future, it would make more sense to see a team land in Calgary or Vancouver, than here.
Fourth, Toronto is not good at supporting any teams outside the Maple Leafs. This isn't even a hockey town as proven by the resurrected Marlies, Ice Dogs, Battalion, and Majors. Rogers can't be filled for the Argos or Jays, and the Raptors no longer sell out the ACC and we've already lost an Arena Football League team there...how long would we support the NFL when it loses its luster? Again, the NFL would want a market that supports the team like the situation in Calgary.
Fifth, too much competition for the entertainment dollar in Toronto. Not only do we have the NHL, NBA, and MLB...three of the four majors...we also have a large theatre district and other entertainments that would pull away from the NFL. Realistically, a new NFL team wants to be the main community focus (see Carolina and Jacksonville as good examples).
Sixth, Canadian owner Pat Bowlen, in Denver, has already come out against Canadian franchises a number of times. He's not the most vocal owner, but Denver is a model franchise and he is well respected amongst his peers.
There are more reasons...many more...but I think that covers the big ones.