-People are forgetting that prices of SD, Micro SD cards, SSD, USB Flash...are constantly falling like a rock.
-They can have a range of sizes of SD cards.
Majority of Nintendo Wii U games are less than 8GB, it safe to say that majority of games on next hardware will be less than 20GB, so 32GB SD would be more than enuf for Nintendo games, but they can use 16GB and evan 8GB for some games, and for really big games like a Xenoblade X or some 3rd party it can be used 64GB.
-What's with all this, "what about patches and DLCs", what about them!?
You can clearly see how are they managed now on current gen, I don't see why would be different on next Nintendo console.
SD slot is very cheap, much cheaper than optical drive, that could affect on price of console.
Also maybe Nintendo could have little cheaper digital games on eShop than physical SD based games.