Nintendo have routinely shown they operate much differently from Microsoft or SIE/Sony. They have the longest legacy in gaming and the most beloved IP among the platform holders. Their games also tend to sell the most relative install base out of basically every publisher who isn't Take-Two, and they accomplish that while staying exclusive to their own hardware.
For Nintendo, hardware and software are intricately connected, joined at the hip, and inseparable. In other words, if Nintendo stopped making their own hardware and having their games exclusive to that hardware, they'd just cease being a video game company.
The only likelihood of a Nintendo game on other platforms anytime soon, IMO, is if they make some new GAAS/live service IP farmed out to a 3P studio, and a 3P publisher to publish on non-Nintendo systems. It'd be the equivalent of their mobile strategy but in this case, not even acting as spinoffs of actual franchises Nintendo make for their own hardware. And after 3-4 years, they'd end support for the game since it'd have served their needs.
Have you ever actually looked at, like, ANY Nintendo fiscal statements? They are not like SIE; they aren't reliant on 3P sales revenue because most of their software revenue is in fact from their own 1P titles. Besides, how many 3P AAA publishers really supported the Switch? Not many. Meanwhile, indie games are always going to cost cheaper and make less, and most indie games really don't sell a ton of copies (on any platform), because there are simply so many. The Undertales, Balatros, Among Us, Schedule 1s etc. are like the top 5% or maybe even top 1% of indie releases when it comes to big market sales.
You're also overestimating the money NSO brings in; last I checked, NSO sub counts were roughly in PS+'s ballpark, but NSO is WAY cheaper, at $20 a year for the base tier. NSO+ costs more, and it's had some good adoption, but it'd only be a subset of the primary service's sub rate.
So basically, you've completely misconstrued Nintendo here, because they're the one platform holder where exclusives actually are the main reason to buy their hardware. And it's been that way since the N64 (I'd argue since the SNES, but that system did get tons of mainline 3P support for its day, more than any other 4th-gen console).
This is a great point actually. Even if by some chance Nintendo stop making hardware, they can easily just switch to an app store of their own on other platforms like iOS, Android or even PC. They'd probably do something like require semi-regular login syncs for games (even single-player ones) to check for piracy or anti-cheat stuff, and tie all access to the account.
But they could easily make that transition if they must. And, it still retains all integration & synergy within their own ecosystem, even if it's technically accessible on other devices. TBH this is what SIE should've done when bringing their games to PC, but they stupidly gave up on that because they wanted that Steam money.
Now, if they tried introducing their own launcher/storefront app on PC, it'll likely do poorly since they've trained so many people to expect those games on Steam, where they will inevitably prefer to buy them since Steam will have magnitudes more games (multiplat & exclusive) than any PS PC launcher could hope to have.
People like to give Nintendo crap sometimes, but they've shown to be very smart and observant about how to value their IP and their brand, and they've retained the integrity & value of their IPs/brand better than any other company in the business. There's a reason they've become so ingrained in the industry & culture as a whole, and part of it is because they didn't whore themselves out to every other platform or service under the Sun just to get make quick money for pleasing greedy shareholders or because "line must go up".
