With the reveal of the Nintendo Switch, and its use of cartridges to play games, many wondered if backwards compatibility with the 3DS or Wii U would be possible. IGN sent a request to find out definitively, and Nintendo answered with a simple, “No.”
Apparently, “Nintendo Switch is dedicated to deliver a single-screen experience.” which obviously wouldn’t allow the dual screen play both 3DS and Wii U offer at times. Now obviously, it’s very likely that eventually, likely via the Virtual Console, 3DS and Wii U games will work on the Switch, but it won’t be at the start.
With Nintendo stating there won’t be anymore news on the console until 2017, there’s likely going to be a lot more speculation and rumor until they next reveal.