Canadian military?

So we thought that we had 4 years left for SO's contract, only to find out that he only signed a 5 year one. So he is done in a year and a half. We've been posted to Cold Lake for 2 years, and now he can request a new posting. He is considering signing another 5 year contract if we get posted to Trenton... How likely would you think it'd be to get posted there before his contract is up? What is your experience with this?