The Nintendo Switch will have Micro-SD Card Support and the size limit for the Micro-SD Cards is quite high apparently.
Where the New 3DS supported Micro SD up to 2GB and Micro SDHC up to 32GB, the Nintendo Switch development hardware supports Micro SDXC cards up to 128 GB in size. It is currently unclear if this upper limit will be reduced on the retail model, but the development model of the Switch does support running software directly off the Micro SD card as you would off the internal memory or a game cart.
In addition, a source close to the production of the Switch reveal trailer has informed us that the Micro SD slot on the Switch can be located underneath the handheld’s kickstand on the model shown in the reveal trailer.
This is great news, as it ensures we can store a lot of games on the console if you have a high capacity Micro SD Card.