I’m not sure what else this could be? Of course, patents don’t always (nor often) confirm something is coming (we all remember the original NX patent from 2015 lol), though this does strengthen the argument that DS/3DS is coming to NSO soon.

Dual Screen mode is definetily the extra Screen that can attach to the system.
On docked mode would work as the new Wii U.

NintendoLand Deluxe make it happen!

Not the same without a 3D display though.

With the Switch 2 having a 120hz panel, they in theory could support shutter 3D glasses to replicate the 3D experience.

The input lag on all of these games make them unplayable for me. I don't know if it's because I own the originals and play them on their native hardware/CRT, or what, but it's almost instantaneously a turn off whenever I attempt to get with the times. And that goes across the board. Doesn't matter if it's Xbox or Playstation. The input lag kills any fun I might have had with them.

DS games? I can believe it. 3DS games however are still shiny enough to get the HD remaster treatment.

That’s what I thought, for instance, about GCN games — e.g. Pikmin 1+2, Super Mario 3D All Stars, Metroid Prime Remastered, Paper Mario TTYD Remake, etc.) — but lo-and-behold, GCN got added to NSO (and not only that, but without any subscription price hike). Nintendo can be a bit unpredictable at times. I think DS is coming in the near future, though 3DS is not impossible maybe 5-10y down the line.

The original Switch could link up other units to make more than one screen as shown with Mario Party. I just figured Nintendo could figure out a way using Bluetooth to dual render and wirelessly send one image to the TV and the bottom screen be on the Switch 2. Similar to Wii U. DS/3DS would not take that much resources. Also in portable mode just use something similar to a flip grip.

Not the same as most of the 3DS SKUs granted but there were 2DS models. If Nintendo could do that back then, it's more than understandable to limit 3D support to glasses or none at all. 

If Nintendo is experimenting with multiple screens, DS and 3DS on NSO seem like a given. Not soon, though. 

Vertical mode. 3D Shutter Glasses.
Just need a cover to have the joycons on the side... And win win for 3DS emulation.

Not ready to relinquish my 3DS and Physical library just yet... That 3D experience is hard to get anywhere else outside of PC.

So something like this?

Retroid Dual Screen Add-on (for Retroid handhelds)