According to Nintendo President Tatsumi Kimishima, Nintendo Switch controllers backwards compatibility may be happening when the Switch comes out, and if implemented will allow Wii U Pro controllers to work on the Switch, though nothing has specifically been considered yet, and even then Nintendo may not want it in favor of the Joy-Cons.
Currently, the Nintendo Switch isn’t backwards compatible for games that were on the Wii U yet, the Switch is more powerful than the Wii U and thus games from the Wii U can actually be ported over to the Switch.
This is actually happening already, as Nintendo plans to port things like Splatoon over from the Wii U, along with a number of other Nintendo Wii U games.
Nintendo Switch controllers backwards compatibility, however, is another matter; currently the Switch can’t work with older Nintendo controllers, meaning that the Wii U Pro controller won’t work with it.
As we said above, Nintendo may not even want a Wii U Pro controller or any similar controller to run on the Switch, especially since the Nintendo Switch appears to rely greatly on the Joy-Con controllers, the vibrating feedback that they provide, and more.
While people may feel more comfortable with a Wii U Pro controller (especially over the rather awkward Wii U gamepad that was the first real way to play the console), Nintendo may be thinking more motion-based controllers like the original Wii motion controllers, or other controllers that will be useful with the console’s motion-based gameplay, such as 1-2-Switch, the launch title that’s going to be making heavy use of the Joy-Con controllers.
The Nintendo Switch will be releasing on March 3 worldwide, so it might be at least a few months after the console actually releases before Nintendo announces whether the Nintendo Switch controllers backwards compatibility is going to be a thing.