I don't agree with you on these points - my experience of console/PC gaming vs phone/tablet gaming is that phone/tablet gaming experiences tend to be very shallow drop in/out experiences compared to what is available on console or PC. Even the heavily curated Apple Arcade doesn't have any good examples of this that I've seen.
I've not seen a Breath of the Wild, Super Mario Odyssey, or even Mario Kart 8 tier experience on mobile. Given that, I don't see Nintendo, Sony, or Microsoft abandoning their dedicated hardware any time soon. Sales are still strong, and there's no evidence of consumers abandoning these consoles for mobile-led gaming as yet. Maybe it'll happen, but I'm skeptical. Playing big gaming experiences on a phone display with phone controls (or worse, some kind of bolted-on-extra controls) sounds like a miserable experience to me.
You mention games like fortnite a bit in other comments, and the court documents from Epic's case show the revenue share for fortnite is not in favour of iOS or Android - it's PS4 by some margin - https://cdn.arstechnica.net/wp-content/uploads/2021/05/apple...
edit: for Sega, given you raised that example - Sega had a series of missteps in the console hardware market that Nintendo don't have any real analogue for - the Mega CD, the 32X, the Saturn (outside Japan) - all of those led to losing consumer confidence. And then, the Dreamcast failed against the behemoth that was the PS2.
The closest I can come to this for Nintendo is the Wii U, which was also a pretty significant flop, but the Switch has had them bounce back in a really strong fashion.