UPDATE:
It has been reported by Nintendo Japan that Super Smash Bros. Ultimate will run at 1080p 60fps docked and 720p 60fps portable. You will also be able to use the Wii U’s GameCube controller adapter on the Switch.

Nintendo of Japan confirms that Smash Ultimate runs at 1080p 60fps docked, 720p 60fps portable, and is compatible with the Wii U’s GameCube controller adapter. pic.twitter.com/SoCDZ5LMvg

— Kyle McLain (@FarmboyinJapan) June 12, 2018

During Nintendo’s E3 Direct they finally unveiled Super Smash Bros. Ultimate on the Switch. Every fighter in history is participating in Ultimate. So that includes the Nintendo 64 version of Smash, Melee, Brawl, and on the Wii U. This title also brings the return of Ice Climbers, Snake, Cloud, and a surprising new comer in Ridley. After all this there will be 65 characters in Ultimate and it looks like there will be more added by looking at this official Smash Bros. site. 
The starting roster is as small as the Nintendo 64 game, but of course this will be the biggest roster we’ve seen in a Smash title so you’ll be able to unlock a lot and of course we can’t forget about future DLC.  It was noted that each character has been overhauled with new abilities and cosmetic design, which was expected to make the design feel more dynamic. There was also a new feature that was Echo fighters, which is based on characters with unique outfits.
It was also announced that you can use the gamecube controller with Super Smash Bros. Ultimate.
Super Smash Bros. Ultimate will be releasing on December 7th, 2018.