2-4 years was the norm at the peak period before C24, C24 drastically reduced the processing time to below 12 months right after implementation and then it gradually converges to 12 months now. C6 will suddenly move back the processing time to 4 years innitially and then will gradually converge to 2 years after a while. Think about this, Canada accepted 300K of immigrants each year in the past few recent year, the built up due to C24 and C6 now makes around 1 millions of people more becomes eligible (counting those who are able to use 1 year pre PR now). The number of citizenship judges have been reduced without replacement due to people retired and few are added. With 1 millions of applicants increased, the wait time will be at least 3-4 years for citizenship oath appointment. This will mean that right after C6 new residency rules take effect, one would need to wait at least 4 years for processing in routine cases, for non routine, it can be up to 10 years