This is Furukawa. At today's Corporate Management Policy Briefing, we announced that Nintendo Switch software will also be playable on the successor to Nintendo Switch. Nintendo Switch Online will be available on the successor to Nintendo Switch as well. Further information about the successor to Nintendo Switch, including its compatibility with Nintendo Switch, will be announced at a later date.
I'm guessing this is from consumer pressure, until the Switch people definitely bought more physical copies of games and the minority of people got digital versions of DS/Wii-U games, but now so many people are using nintendo online and buying virtual copies people probably would not buy the next console if they had to buy the games they liked again.
I mean, Nintendo have often been fairly good with back compatibility.
If the architecture and form factor of physical media isn't really changing, there's not a lot of need to block older games from running.
They're already on ARM, and there's not much better for mobile gaming and GPUs have been fairly similar for a long time now.
The more interesting question is: will the Switch games get a performance boost on Switch 2? And it's probably going to depend on the game. I'd imagine they'll test a lot of the more popular titles, and anything with issues just gets it disabled until the developer patches it. It'd be nice to play TotK at a decent frame rate. Impressive as it is, it certainly chugs.