With the way Nintendo is bundling older games to the Switch Online subscription, we will at some point get to where DS and 3DS games are accessible this way. But for now, the Switch device itself, or indeed its sequel, doesn’t quite do dual screens. A recently granted patent may change that.
Published via the USPTO, the Nintendo patent describes possible dual screen implementations for what looks like the first Switch. Though weirdly enough, the diagrams look to be pointing at the requirement of other units of the Switch to serve as the second screens. TVs connected to the first one, often labelled as the Parent Apparatus in the patent, don’t seem to count.

Following that are images describing what will appear on the first and second screens. If you’ve gamed on the DS and 3DS, these will look pretty familiar. The primary screen shows gameplay as usual, while the second screen shows auxiliary info like a map or menu.
If you don’t have access to something that can serve as the second screen, worry not. The patent also shows two possible ways it can squeeze the function of two screens into one. First is simply picture-in-picture, where the map becomes a mini-map and sits in a corner. The other allows you to have the display switch between the primary and secondary screen with a button press, though it’s unclear if this is an on-screen or physical button.
Judging purely from the patent, it seems strange that the second screen needs to be another switch, and not just a TV. On one hand, the Switch and Switch 2 needed to be docked to output to a TV. But on the other, DS and 3DS games never needed the primary screens to also be touch screens. But as confusing as the patent is, it’s best to not take it as a sign of things to come.
(Source: USPTO)