It would be nice to think that CF Champlain has been proactively looking for a replacement for Sears (the writing has been on the wall for several years after all). I agree with you that Canadian Tire is not an acceptable option, and given CF Champlain's pretentions of being a "fashion mall", I doubt that they would consider this.
I think the Sears space will either:
1) - become HBC
2) - become Simons
3) - be broken up to accommodate several smaller retailers, possibly including a couple of smaller anchors like F21 and Zara.
I really think Cadillac Fairview
does have something up their sleeve. This space will not remain vacant for long. It could even be part of a larger mall revamp........