It took us 2 years to put QEII on the banknotes (& what a devilish enterprise that became!
).
Great Britain & Jamaica took 8 years. I think the average was 2-4 years. The main thing is it doesn't happen overnight.
I don't think it will take 2 years since the technology is different today but I would guess it will take up to 2 years. I suspect the transition will depend on a number of factors (when the BoC feels like a refresh is in order for the $20).
The vertical $5 was supposed to come out in 2021 wasn't it? It has taken forever. I think with the successes of the Better Than Cash Alliance, Covid & CDN's rapid acceptance of going digital (less need of cash), self-check outs imposed on us, there won't be any rush- but I could be wrong.