Part of me wonders whether it's actually The Witcher II which is being ported to the Switch, and it's being misreported as III. Considering that II already has a 360 port, it'd probably be easy to bump its resolution up to 1080p, maybe make a few other graphical improvements, and slap it on the Switch.
(Then again, they said the same thing about Saint's Row the Third, and look how that turned out...)