Petréa Mitchell, in The Shape of Worldcon Bids to Come on Con-New.com, points out that there are 7 active Worldcon bids — and right now every one of them is uncontested.
How long is that likely to last? Her answer is worth reading, and the comments are provocative.
I’m not sure you can predict Canadian worldcon bids the same why you might predict them for East Coast or West Coast. There isn’t a Canadian fandom as such, but three or four locii who have very little in common. It’s more a question of when you think the Toronto group might try again — considering luckwarm reception of Torcon 3 and that the group launched a new annual con only just last year. Montreal? I don’t know if anyone can read their minds. BC? Doesn’t seem likely at the moment. Nor does “The West” — Calgary, Edmonton or Winnipeg. If I had to put money on it, I’d guess fandom will hear of another Toronto bid first, but not for a few years, and Montreal would be my second guess.