That would make no sense unless there is no BC. Why is this something they should do?
I mean, they did it for MD1 despite BC. If they're doing dual versions, targeting one for each hardware with inter-compatibility could be an interesting sales experiment with the mainline with the potential for more involved differences and possibility to encourage the fanbase to upgrade sooner while still not leaving out the gigantic Switch base. Gamefreak could have their cake and eat it too.
What's going to be NSW2's Skyrim? I think Elden Ring or Baldur's Gate 3 or both.
BOTW, Skyrim and Xenoblade 2 tag teaming year one really helped define the diverse and sizable global RPG audience on Switch, which just continued into the subsequent early years in 2018-19 (DQXIS, Octopath, Dark Souls, TW3, DOS2, FETH, MHGU, Diablo III, Pokémon LG, etc). On the lower end I think the consistent early support of NIS (plus Falcom ports) and Gust in particular also helped attract and define the audience for the AA side of the genre on the platform, not to mention indies generally doing their thing to much success (Golf Story, Undertale, Stardew Valley, etc).
In terms of a game specifically like Skyrim, aka: a huge CRPG coming to Switch 2 in Year 1-ish, I think we'll see conversions of Baldur's Gate 3 (Larian), Cyberpunk 2077 (CDPR) and Diablo IV (Blizzard) specifically in or near that timeframe. Nintendo worked directly with all 3 studios on Switch 1 to bring their games over and I expect a repeat all around this gen has been in the works awhile. The only one off the table is really Bethesda with Starfield, but even there we'll probably still see Skyrim get a native release/upgrade patch and potentially other catalog Bethesda releases (Fallout 4, Oblivion remake, ESO).