The latest rumor is intriguing.
Multiple online stores in Asia have listed a physical copy of The Witcher 3: The Wild Hunt for the Nintendo Switch with a September 2019 release date.
Those listings is suspicious considering online stores in Asia are notorious for listing games that doesn't exist.
The second red flag is the fact that the much more powerful PlayStation 4 and Xbox One consoles struggles to run that game at 30 FPS.
A physical copy would require complex optimizations that would cost a lot of money to achieve without help from Nintendo. Would either party approve the investment?
It's possible those listings could be for a pass to play the game for a certain amount of days via the Cloud. Only time will tell.
Update: It was announced at E3 2019 that a complete edition of The Witcher 3: The Wild Hunt, including all of its DLC, will be released for the Switch in both physical and digital form in 2019!