A current big rumour going around is that a title for the Switch 2 will be an enhanced port of Breath of the Wild. The Sega-leaker Midori, who has a currently flawless track record from everything I've seen,
mentioned that there's a project at Nintendo called "U-King-O", with U-King being the original BOTW's codename. Similar enhanced ports in the past, like Captain Toad Treasure Tracker, have had the same naming scheme ("Kinopio" for original release, "Kinopio-S" for the Switch port). Pyoro, another leaker more focused on Nintendo who also has an essentially perfect track record,
has backed this up. That ties in with another current rumour about the Switch successor's codename prior to this,
where some major Switch dataminers have suggested the Switch 2's codename was dropped by Nintendo in a version update, and that it was stealth "leaked" on Famiboards as something like "Ounce", beginning with the letter O. I think it's silly to be so coy about a codename leak of all things but it is what it is. All that goes back to a major news piece about the Switch 2, where
both Eurogamer and
VGC reported that the system was demoed at Gamescom with an enhanced version of BOTW alongside a showcase of The Matrix Awakens on the hardware.
Basically, would all suggest that that enhanced Breath of the Wild tech demo might be an actual release for the Switch 2, and given pretty much everything has supported the Switch 2 having backwards compatibility, it indicates Nintendo, like Sony with Spider-Man and The Last Of Us, is willing to do enhanced versions of their previous generation's games on the new console even with backwards compatibility. We have no idea what the port could contain beyond enhanced graphics if this all pans out, but it would at least be a point against the argument of why Nintendo would bother releasing a game already available for the console again. Of course, Smash has other factors to consider even if this is all true, like licensing and the fact that it wouldn't get as much out of or be as marketable on the basis of enhanced visuals as a game like BOTW, but it is interesting.