Isitt will run for mayor in 2018, I'm almost sure of it.
Other then that, its hard to pin down other candidates. Lisa Helps could run again, but if to many qualified candidates enter, especially on the left, she risks being squeezed out.
A very likely person (who I'm surprised no one has mentioned here) is Marianne Alto. A lot of NDPers would prefer her (Shes a fairly moderate, average Dipper type, unlike Isitt) and if no one qualified enters on the centre-right, a lot of Liberal/Conservative types would go for her. Less then a year ago I asked her directly if she would run for mayor, and she confirmed that she is thinking about it. With the things I've been hearing from my Lefty-friends, she will be running for mayor.
I hope the business community also puts up a candidate. I've heard rumblings of right-leaning slates being planned (actually two separate ones organizing against each-other) put I'm unsure if either plan to run a candidate for mayor, or just candidates for council. I think the most likely right-leaning people to throw in their hats would be Bruce Carter or Bruce Hallsor. I doubt Chris Coleman will run for mayor as any sort of right-leaning standard bearer, firstly because he doesn't have the organizational capacity to realistically win, and secondly because though a centrist, he tends to lean left more often then right.
Finally, the dark-horse candidates. The most likely type I see with any chance of winning would be a tea-party, anti-tent city lets clean up city hall type. The most likely candidate is Shellie Gudgeon, who despite sitting on council maintains something of an anti-establishment image.