That would lead to PC being the only platform, cause no one would have incentive to buy a Console. Don't get me wrong I'd love that, but I doubt Nintendo will ever put their games on PC.
I think most of people buy consoles because of three things:
- It's cheaper
- It's accessible in the sense you don't need to bother with specs and upgrades
- It has an habit to play on consoles, and people don't like changing habits
Even if all games were on PC, I don't think consoles would stop selling. I mean, Xbox are still selling 50 million despite all their games being on PC as well
If Xbox can sell 50 million with a brand nowhere near as big as Sony I can pretty much see Sony selling their 70-80 million regardless of their games being on PC or not
As for Nintendo, they are the only publisher selling handhelds, that's will secure their 40-50 million no matter what happens. But I agree, if they release their major games on PC their market share would suffer because there would almost no point buying Nintendo home consoles to play a thing that can be played elsewhere, their consoles are far too underpowered to justify a purchase for people who only or mostly plays as home console and could play their games elsewhere. I personally would still buying because I like handhelds but if I was a console gamer I would never buy a Nintendo again if I could play their IPs on PC, specially because they never require high specs, even my entry level PC can play games better than my Switch