Final Fantasy XV, Nioh, Nier, Yakuza, Kingdom Hearts, Tales, Resident Evil, etc every big Japanese game outside of a Dragon Quest Dynasty Warriors game is skipping Nintendo hardware this year. Even Monster Hunter is skipping Switch for 3DS (lol)
As for the first thing you said, I don't even know what it means. Japanese people don't play on consoles. That's all I know.
a) Monster Hunter team heavily hinted that, yes, MH will be on Switch eventually.
b) 3DS is a Nintendo system
c) Nintendo itself is one of the biggest developers/publishers in Japan
d) Look at actual game sales in Japan. Look at where the million sellers are in that country.
e) Sony is not looking like it will follow-up Vita, i.e. Switch is alone in the portable space.
f) Yes, 3DS sales are down from DS but it has outsold PS2 in that country. The sudden disappearance of portable form would be a huge drop-off for that console market.
g) PS4 is only tracking on par with PS3. It is not going to get much past 10 million in that country. It is not like suddenly stationary is taking off again to make for the slack of no more portable console.
Also, if you don't get the first part...the idea that the Japanese console industry is dying does not mean that it is already dead and that Nintendo being gone would change nothing. So, basically, you have no point when you say "but phones."