Nintendo filed for a patent on a disc-less system with the United States Patent and Trademark Office in February 2015.
“An example system includes an internal hard disk drive storing a program and/or data, a communication unit transmitting/receiving a program and/or data via a network, and a processor executing a program stored in the hard disk drive to perform game processing,” the application reads before getting to the key part: “The example system is not provided with an optical disk drive for reading out a program and/or data from an optical disk.”
Most likely we shouldn’t feed to much into this, it could be some time before this is made to completion. Interestingly enough when you think of card slots don’t you kind of associate that with a SD card? Interesting to say the least and worth keeping an eye on. Could this be the NX? Doubtful but completely in the realm of possibility.