Actually, they may be near the point of having depleted the current stock of "Printed in 2006" $5s. APL may most likely be a possible changeover prefix, but then again there are still many APKs that have yet to be distributed (according to the Wiki lists, the current high for APK is still in the 1.8 Million range). Once that is done, they will probably print the new stock with the Carney signatures and ship them to banks across the country.
I certainly hope they don't release them just after Christmas - or it will likely be April or May 2009 before they see the light of day in some Canadian provinces.