I got R10 in December, so Canadian R's are in the teens. As of March 9 the P numbers were reportedly at 143.
I expect a lot of the R's will switch to S's. There's a possibility that an R number might go down, but obviously not by much!
If you're very low on the P list, your number will probably go up. But if you're way up on the list, it will probably go down. Either way you're going to get your car at least as early as before, and possibly much sooner.
I believe the extra three months is the time required to get the car certified for sale in Canada. If they're late it'll probably be the fault of Canadian bureaucrats.