Why would it be?
Never in history has a single multi platform game had that great deal of impact on any dedicated console, let along being crucial to its survival.
The most important games for Switch 2 will be what it already has: an inheritance of a steady stream of dozens of games per month from the first Switch. And those key releases proven to drive hardware sales: Mario Kart, Animal Crossing, Zelda, Super Mario, Pokémon, Smash Bros, Switch Sports, Switch/Ring Fit, Mario Party, and other game franchises that can sell multiple 15-70 million copies on the console per release.
If GTA6 was as important to Switch 2 as the question suggests, most of GTA6’s revenue would occur on Switch 2. Mario Kart 8 Deluxe wasn’t essential to Switch’s survival, and without a price drop and only trivial discounts during holiday specials, it has sold near 70 million copies on Switch alone. GTA5 has sold 205 million, most of the volume between 1/3 to 1/2 the price of Mario Kart 8 Deluxe - also multiplatform across three generations, including non-dedicated platforms like PC.
So, if GTA6 was crucial to Switch 2’s survival, it would be by far the most important platform for the game. It would also mean Rockstar has been stupid to ignore Nintendo consoles.
I describe myself as a little dose of toxic masculinity.
