>>19737416I would like to see Mewtwo back, but I wouldn't count on it. Even Jigglypuff barely made the cut in Brawl.
>[citation needed]Pic related is the internal list of Brawl. The top row is an accurate representation of when all the characters, including the cut ones, were added to the game.
The first 11 are all veterans from the first game. Following that, every character up to Ganon were veterans from Melee. After that you have Brawl's newcomers.
At the very end you have a few characters that made it into the game and a bunch that were cut. These are all characters that were very likely deemed unimportant and expendable early on in developement. Notice that Jigglypuff is in that section.