While I agree that Switch is starting to saturate in Japan, that should only result in mild declines year over year. The only thing that may cause a cliff for the Switch is the successor, if it's fully backwards compatible.
Don't forget what happened with the DS, where the year before the 3DS released it sold another 20M+ and was over 140M LTD. The general consensus had to be that it would outsell PS2, but after 3DS launched, DS sales practically stopped, selling less than 9M that year and around 4M from then on. Those last couple years the DS was even being outsold by the Wii in its late years. And that's with the 3DS being overpriced at launch and not selling as well overall as the DS did. (All numbers and comparisons here worldwide)
Switch: SW-3707-5131-3911
XBox: Kenjabish
