I posted earlier that the Switch supported up to 256GB MicroSD (actually MicroSDXC) cards, well now Nintendo has confirmed that it will support up to 2TB when they become available. This was in an official statement given to GameInformer.
|“Nintendo Switch is compatible with the SDXC standard, which supports up to 2TB. (Note that 2TB cards are not yet on the market, but the system will support them when they are.)”|
As noted, 2TB SDXC cards aren’t available yet, as the largest MicroSDXC card is currently 256GB while the largest SDXC card is 512GB.