During today's Super Smash Bros. Ultimate Direct, series creator Masahiro Sakurai unveiled new playable characters (including Echo Fighters), new game modes, and more. At one point in the presentation, he also highlighted some of the rule changes in Smash modes, including the fact that you now choose your stage before you select your fighters. During this segment, he revealed an exciting new feature that's likely to shake up the game quite a bit.
Players will now have the option to toggle on or off a chargeable Final Smash feature. When this feature is turned on, each player will have a meter that slowly fills up. When that meter is full, a fighter can unleash a weakened version of their Final Smash. This will keep battles exciting and dangerous, but there is a limitation. Two (or more) players cannot unleash their Final Smashes simultaneously.