Before we went decimal in the 70's, we were quite used to seeing George V's and George VI's heads on our coins. There were even a few Victoria and Edward VII pennies (Edward VIII didn't hang around long enough for many coins with his face to be minted). I assume the same will be true with notes. Existing currency will continue to be minted and printed, and new stock will gradually replace it.
All around the world? Not really. GI seems to be an almost entirely American thing. It's not very well known in the UK, and never seen on TV. According to Wikipedia it's only ever been released on Region 1 DVD.
Although Wikipedia says "Around 1560, an Italian couple named Simonio and Lyndiana Bernacotti made what are likely the first blueprints for the modern, wood-encased carpentry pencil."
Well, that's a new word I learned today!