Except Toronto needs to build a new stadium and is much less likely/able to build one on spec than LA. The only way they build one is if they know someone will buy the Bills and commit to moving them, which is a much less likely prospect now. Can't build the stadium without a team, can't get the team if they don't have a stadium.
And as for LA - the only city, by the way, to lose not only two but THREE professional football teams - I think their time is coming, and sooner than 2020. There aren't many teams left out there without a new or renovated stadium, so now that that purpose has been served, the NFL can turn its attention to getting a team back into that market with a true Super Bowl-ready stadium. Once LA goes, what's left? London?