Earlier quoted context omitted.
> They will not go back to cartriges obviously It does indeed use cartridges: http://www.polygon.com/2016/10/20/13344618/nintendo-switch-n...
Aren't SD cards and cartridges different? I thought that cartridges used ROM while SD cards can be written to.
With the modern carts, it's all flash memory - both the game binary and any user data can coexist. That said, it's much less common than in the NES era, but not unheard of, to incorporate custom hardware on the cart. For example the DS Game Card[0] has an infrared variation. With this change the overall performance model now is guided around working with flash memory - you have big mass storage, longer load times, and don't get to do any fancy bank-switching tricks or rely on an additional co-processor or an extra RAM bank.
[0] https://en.wikipedia.org/wiki/Nintendo_game_card#Nintendo_DS...