What could the Switch2 'Gimmick' be?

[Leynos]

I said this before but the ability to stream the game to the TV while also having the game displayed on the 8-inch screen. Allowing for Wii U ports. DS ports. Local multiplayer.  I'm not saying they replicate Wii U functionality in their new games. I am not saying this is the main gimmick either—just a bonus ability.