Assuming games will be tied to a Nintendo account and not a system, people are now assuming you can buy Super Mario World, for example, and it will be yours forever.
However, as we know, Nintendo can already identify that you own different versions of the same game and don't offer them to you across other platforms for free. They may offer a discount if you own one of the versions, but they aren’t ‘cross buy’, so buying Super Mario World on 3DS does not entitle you to the Wii U version.
It’s therefore feasible that we could buy a Switch version of Super Mario World, but not necessarily have access to the ‘Switch 2’ version of the game. (Publishers on PSN do this sometimes, such as with Final Fantasy 10. PSN will recognise you own the PS4 version of the game, but you still have to buy it a 2nd time if you want to play it on Vita).
Just food for thought.