Doesn't make any sense to talk about traditionally what Nintendo does with home consoles when they've never had a home console selling close to 30 million units a year, let alone in years 4 and 5, and with no price cuts, that has a decent chance at selling over 150 million systems, and a new round of systems did nothing to slow sales down. There is no precedence for these kind of sales, so of course you can't just say oh they'll replace it at the normal time. That'd be crazy to do. "break their entire history as a gaming company"....that statement has no meaning. It breaks their company that they have an insanely popular system that will last longer than their previous systems.....riiiiiight.
If your logic was true, then they would have done the same with the last system that sold insane, the DS. It released November 2004 and sold over 150 million copies. It lasted 6 years and 3 months before being replaced by the 3ds. Why didn't Nintendo delay releasing the 3ds, if your logic holds up? Why not keep pumping out games for the DS in 2011 and 2012 and beyond, like you suggest the Switch should do with lasting until 2024 and beyond? The Switch won't pass the total sales of DS ever, let alone in the ridiculously quick time-span DS did. It's a fantastic selling system, one of the best ever, but it isn't some unprecedented performance that will change what Nintendo has been doing for decades.
Also, eventually, software won't be able to be as creative and the fans wil get bored of the latest entry in series that aren't evolving enough due to the limited hardware capabilities of either the Switch or the slightly better hypothetical Switch 2. How many times have developers talked about the secret sauce of *insert popular game* being the new found capabilities of whatever new system they produced the game for? And how many developers have complained about older hardware? There is no way hardware and software sales for Switch will be in 2022 what they were in 2021/2020, and 2023 will tank hard (Pro or not). Most people won't even be aware of the Pro model, and of the chunk that are, most won't care enough to upgrade. There will be like 10-15 million happy super nerds buying a pro when Nintendo could have released the next actual console and sold twice or triple that amount to all consumers. We need to stop hoping for Switch 1.5 and start hoping for Switch 2. That will be a glorious device that we can all buy, not just super nerds who care about tiny bumps in power.