If you still haven't purchased an SD card for your Switch, you better list that on your plans, since Nintendo of America told IGN some of the upcoming games will require that storage expansion. So far, NBA 2K18 will be one of such games. Interestingly enough, in case you purchase a game with such requirement yet don't have an SD card, apparently you won't be presented with a screen saying you'll have to in order to play, instead you'll be able to play portions of the game. "If you purchase a physical version of a game that requires an additional microSD memory card, you will be able to play a portion of the game right out of the box (for example, specific levels or modes)"
a representative for Nintendo of America told IGN. However, the remaining data has to be downloaded.
I guess this was already expected, considering this console is expected to run games almost on par with the competition's home consoles, it wouldn't make sense to force a limitation to the games simply based on storage issues (fortunately Nintendo have learned from the N64 and Game Cube mistake), plus you'd need one anyways if you wanted to have more than an handful of games. I also appreciate Nintendo's approach of still letting players to enjoy part of the game which can be helpful if, for example, the parent buys the game for the kids not knowing it requires an SD card and then the game can't be played until that second purchase.
Still, I'm not too sure about having to download [large] files after buying a physical game on a console of this kind; also when you have to buy extra storage to play certain games (and I'm sure it will eventually become the norm) means the actual cost of the console ends up being even higher - Nintendo might not feel the need to lower the console price right now while it's selling like hot bread but for reasonable buyers, it's inevitable.