Nintendo Switch Won't Play Physical Wii U or 3DS Games
Looks like your Wii U discs and 3DS game cards will not work with the Nintendo Switch.
In response to IGN, a Nintendo representative confirmed that Wii U and 3DS physical media will not be backwards compatible with the Switch.
IGN went on to ask if there would be any form of digital backwards compatibility for Wii U and 3DS games and Nintendo responded with, "nothing to announce on this topic," and "we will make additional announcements about the Nintendo Switch hardware later, before the launch of the console."
When asked if the Switch could ever be used as a second-screen experience, similar to the Wii U functionality, Nintendo said, "Nintendo Switch is dedicated to deliver a single-screen experience." Therefore, it appears that the Switch will not be able to take advantage of certain Wii U features, such as having a map or HUD display on the bottom screen.
The Nintendo Switch was announced last week, but Nintendo has made clear that they will not release any more information about the device until 2017. For now, we will just be speculating and over-analyzing the same trailer until the turn of the new year.