Even if its technically possible, why would you want that? I recently bought a Gsync monitor and I can barely tell the difference between 60 and 120fps, while I had to use the lowest graphics settings to hit that 120fps.
Everyone's different, but personally I see a huge difference between the two. Of course it also depends on the game. It would be great to see it for Smash and Kart, but I would have a really confused look on my face if they made an Animal Crossing game in 120fps.
And we haven't even talked about variable refresh rate yet. I probably should have brought this up in the OP since it's even more likely to be in the Switch 2 thanks to it being built in to HDMI 2.1, but with variable refresh rate a developer doesn't even need to make the choice between 60 and 120. They can target somewhere in between, or not even target anything. Again that choice will depend on the game, but especially when paired with VRR it would be silly to not at least support higher refresh rates.