TOTK is putting up huge numbers considering how Voucher heavy (aka digital heavy) it will be with that price. Retail + Digital launch weekend is situating in 1.5-2.0M range for JP.
Outside of Japan I expect it to easily pass Pokemon SV's ~6M figure and do 8-8.5M. If Japan hits the higher end of that above range, it will open above 10M worldwide launch 3 days and beat SV.