Nintendo has recently announced Pokken Tournament DX for the Nintendo Switch and according to its official website (via Nintendo Everything), it mentions that the Wii U controller will be compatible with the game, so if you already own the controller and don’t plan on buying more accessories and peripherals for the Switch, you can reuse them.
However we should point out that the controller is a wired controller which means that if you wanted a wireless controller then you’ll have to revert back either to the Switch’s Joy-Cons or the Pro Controller. We’re not sure if there will be an updated accessory specifically for the Switch that will launch at a later date, but if a wired or wireless connection doesn’t matter to you then by all means go ahead and use it.
Pokken Tournament DX will feature 5 new Pokemon characters compared to its predecessor and is currently set for a release later this year on the 22nd of September.