Its actually very hard to predict, either way 2020/2021/2022 will all be very close in sales.
I'll go with this year, 2021. It's riding off of last years crazy momentum/demand + has a new hardware revision + other devices on the market are extremely supply constraint.
Next year has big releases but all sequels to games already on the Switch. The Switch OLED doesn't seem like the kind of device to encourage too much double dipping, so I don't expect a major sustained boost from it (not in unit sales anyway) and PS5/Series X will be getting into their stride, stealing some consumers coins come next holiday especially.