Toronto won the Grey Cup in 2012, so it's not like they haven't had recent success.
The CFL is small town. It is enjoying some greater success in recent years, but it will always struggle in Toronto unless they move to a venue that holds 20 - 30K, like Montreal did. Toronto is too ethnic, for lack of a better word, to support football at a frenzied level. The Bills' disaster there should send a huge message to the NFL.
I live in Saskatchewan, where the whole province lives and breathes football. We held the Grey Cup last year and it was like a massive, province-wide party. When it is held in Toronto, it does not garner near the attention or party atmosphere.
So, NFL, stay out of Toronto. It has a massive population but is definitely not a football town.