In the Nintendo E3 2018 conference, among so many reveals and confirmations was one related to the next entry in Nintendo’s fighting game series for Switch. That Super Smash Bros. Ultimate will support the old GameCube controller.
The de facto gamepad for Super Smash Bros. can be used to fight, as can a single Joy-Con or Nintendo Switch Pro Controller.
Through a system software update, Nintendo added support for GameCube controller to Switch last year. That said, in order to use your old gamepads, Switch owners will need the Wii U GameCube controller adapter.
Also, Super Smash Bros. Ultimate shall support all existing amiibo and data from them will be transferable to the new game.
At the moment, no price or any particular release date has been announced but hopefully, we shall know soon enough.