newer doesn’t automatically mean it’s going to sell more. The ps5 is also a newer console and didn’t break the record the ps4 set previously. The Switch 2 is the fastest selling console of all time
The upgrade is only $10, you don’t need to re-buy the games to get the switch 2 versions of the game. You also don’t need the switch online membership for a year to get the switch 2 editions, you just need to be subscribed when you want to play it, like how the Mario kart dlc worked. The year requirement was for preordering the switch 2 through Nintendo
