At the very start of today's Nintendo Switch live event, Nintendo officially announced that the console will not be using region-locking in any way. Now any game for the Nintendo Switch from any part of the world will be compatible with any Nintendo Switch console.
Region-locking is a system that Nintendo has used ever since its first consoles, which ensured that games released in a certain region were incompatible with non-native consoles, for legal reasons. For decades, players have been asking Nintendo to get rid of this system, as it made playing foreign games and sharing games extremely difficult. It seems Nintendo has finally granted its fans' wishes, as the Nintendo Switch will be the first Nintendo home console to be completely free of region-locking.
Source: Nintendo Switch Presentation