In fact, the Royal family is a HUGE money maker for Great Britain. The palaces, and all of the other stuff would not get anywhere near as much tourism if there was no monarch. Then, there is all the kitsch that people purchase (both Brits AND non-Brits).
I would not bet on Charles abdicating. After his great uncle, there is zero chance of that happening. But, if his mother lives as long as her mother did, his reign will be a very short one.
If Canada gets rid of the Monarch, then who do you put in that place? The Prime Minister is relieved of a LOT of duty by the Governor, and by the Royals. I doubt if any P.M. really wants to be the actual head of the government (he really is the de facto head).
Personally, I'd like to see Scotland break off, and become a separate county once again.