I don't think there's usually any activity in new prefixes for small denominations during the first two or three months of any given year. Like I had stated in the thread about the shortage of $10 bills, this time period is also known as the "Winter dry spell" for shoppers. There hasn't been a major shopping event since the week following Christmas, and there probably won't be any major shopping until around Easter time. Then come April, the malls and shopping districts will get busier little by little and remain busy until the week after next Christmas (although there will be some brief dry spells but not as extensive as January through March). I did receive some crisp $10s at a Scotiabank branch during the start of the Valentine's Day rush in 2007, but not this year. That particular occurrence was just simply a rarity and pure luck, as that particular branch was most likely offered them up front.
This dry spell was probably proof as to why the first two prefixes of the 2005 print year of $10s (BEY and BEZ) were first reported in January 2006, and there wasn't a reporting of the BT- prefixes until mid-April that year, and the BT- prefixes came on fast, ending with the BTF prefix - first reported that June. By the time the prefixes of the 2005 print year were all first reported, all I saw in terms of crisp $10s were primarily BEZ's and BTA's. Everything else up until then were BEW's, BEY's, and even FES's.
Now, where was I? Oh yeah...
As for the $5s with prefixes between APF and APK and why they aren't circulating in Canada as yet, hang in there - there'll probably be some more activity come closer to Easter. Trust me, you'll all be in for a treat.
And BTW (no pun intended), the last prefix I saw in crisp $5s was APC back in December.