I think FIK onwards would be the CBN notes, if they exist (but I doubt it.)
What'll be interesting to see is how long it'll take for ATMs to convert to polymer, and whether they'll be mixing up polymer and paper notes. Machines that gave out $50s were pretty much dispensing them within a few days of their introduction.
I have heard that the withdrawal of the $20s won't be nearly as fast as the $50s/$100s simply because these notes don't cycle through the bank as often, and because the BOC would be overwhelmed with having hundreds of millions of notes returned within a very short period of time, while pumping out enough new notes to replace them.