GameShare on Switch 2, that is. It's mysterious. It seems kind of like a marriage of Wii U multi-screen support and DS Download Play. Here's my understanding of GameShare:
A GameShare session needs to be initiated by a Switch 2 with ONE copy of the game. At least 3 Switch 2 OR Switch 1 consoles can then be used as dummy terminals (through the new GameShare app added to every Switch's Home Menu), only capable of control input and video reception. All of the dummy inputs are sent to the Switch 2 host (online or locally), and then the Switch 2 host beams back up to three extra viewports (online or locally), while also rendering its own. (In theory, those viewports could just be clones of the main screen in a single-screen game like Smash. But separate viewports are the more interesting application, by far.) This would allow for the best example we've seen, individual hands of cards in Clubhouse Games, all rendered on the host Switch 2, but sliced up and individually served to each Switch through video transfer for full privacy. This could, in theory, also be done using smartphones as dumb terminals (as in something like Jackbox), but let's not get into that right now.
Back when Wii U was still Project Cafe, I was actually hoping it could do something like this with multiple Gamepads. Maybe Nintendo was even planning something like that, but couldn't make it happen.
There are still tons of questions about this. What is the streaming protocol? What resolution would its bandwidth allow? How high is the latency in local/online? Would it be viable for action games? Even online?
There is SO much potential in this concept. Obviously, the Switch 2 would have some trouble serving up four separate 60fps viewports in something like Mario Kart World, but not in something like Clubhouse Games. Perhaps that host Switch 2 could render 4 viewports in a 4k frame and serve a full 1080p image to each screen (or 720p for the Switch 1 dummies (no offense)).
The games thus far announced for Switch 2 Upgrades are:
ARMS
Big Brain Academy: Brain vs. Brain
Captain Toad: Treasure Tracker
Clubhouse Games: 51 Worldwide Classics
Game Builder Garage
The Legend of Zelda: Echoes of Wisdom
The Legend of Zelda: Link's Awakening
New Super Mario Bros. U Deluxe
Pokemon Scarlet
Pokemon Violet
Super Mario 3D World + Bowser's Fury
Super Mario Odyssey
Kirby and the Forgotten Land
Breath of the Wild
Tears of the Kingdom
Super Mario Party Jamboree
We can easily imagine that the single-player games in this list will be updated to increase performance and/or resolution. The single-screen multiplayer games may also be updated with same-screen GameShare, for tv-less multiplayer sessions. (Maybe Nintendo could even bring the missing Wii U functionality back to NSMB?) But the interesting exceptions are Clubhouse Games, Big Brain Academy, ARMS, and Game Builder Garage.
We already know how Clubhouse Games works. Big Brain Academy could rejigger its multiplayer to work the same way. Game Builder Garage could go all sorts of ways. But ARMS... why ARMS? It already worked amazingly well in split-screen, aside from a 30fps drop in 3-4 player.
Sure, they could improve that framerate and bump the resolution to 4k. But what if they went one step further and cut those frames apart in order to serve each console its own full-sized screen? What if they did the same thing with Mario Kart 8 DX, which runs on the same engine? People have been wondering why Super Mario Party Jamboree only supports GameShare locally, on one board, with 30 mini-games. What if those are the mini-games most suited to surreptitious split-screen play?
Let's take it further. What if Nintendo updated the NSO N64 emulator to do the same trick, enabling, say, four-player GoldenEye or Mario Kart 64 with no screen-peeking? What if the Switch 2 had the power to render four separate GBA emulators and GameShare the other screens to separate consoles?
What if!
But, really, I just want Clubhouse Games 3. And a bunch of virtual board games.
URL to share (right click and copy) 
