Generally the trend is consoles have them initially then drop it. I'd really hope the next console does this as it'd mean they'd need to remake/rerelease new games instead of selling the same ones again
You say that and yet it's not really true.
I'm thinking of all the console that I know are backwards compatible and, other than Nintendo's own trend of dropping backwards compatibility with redesigns of their consoles, the only consoles I can think of that later dropped it are:
- The Sega Mega Drive, which dropped Master System compatibility with the Genesis 3 revision. But tbf the Genesis 3 was a hella cheap budget revision released by the company Majesco under license from Sega and not Sega directly and isn't even compatible with the Sega CD or 32X either.
- The PlayStation 3, which eventually dropped all PS2 compatibility entirely. Which some people say was done as a cost-cutting measure because, even with the high price of the PS3, Sony was
still selling it a a loss (IIRC) and the original models of the PS3 released in NTSC regions literally had PS2 hardware inside it (whereas the PAL PS3s used partially software-based emulation for backwards compatibility - which was to save costs) but yet the actual reason why it got dropped completely was because they were releasing a new budget model PS3 system (relatively, we're talking $399 here) and they wanted people who were going to be buying the new cheaper PS3 system to buy games made for the console and not PS2 games lol (And, of course, the PS3
never dropped PS1 backwards compatibility)
Every other console I know of with backwards compatibility never dropped it.
And really considering how much we know Nintendo wants to keep people in the ecosystem they've built up starting with the Switch, I cannot imagine a scenario where they release a Switch 2 and then a later revision of the console drops it. (Especially so because, in my opinion, it's very likely that we'll have a DS/3DS situation with their next console where they have one cartridge slot that's compatibile with both cartridges and it'd be weird to remove such a feature in that case)