I have a source who gave me some information on Super Smash Bros. You don't need to know the details of that, so I'll just tell you what I know.
-First up, Ridley is a newcomer. He is very unique, and the largest character in the game, a bit bigger than Bowser. When playing on the Pyrosphere stage, Mecha-Ridley will instead be in the background.
-Dixie Kong is another newcomer. She is not paired with Diddy, and is not a clone.
-There are now 3 Fire Emblem representatives - Marth, Ike and Chrom.
-There are 6 Pokemon representatives. The dev team were not happy with this, but GameFreak wanted them. They are - Lucario, Mewtwo, Blaziken, PIkachu and Jigglypuff. Blaziken was not originally planned. He is not a clone, and the only move he takes is Blaze Kick, which acts like Falcon Kick.
-Little Mac, Pac-Man, Mii and Palutena are the only other newcomers I know of. There will be more.
Now for information about current characters:
-The Melee clones do not return, except for Dr.Mario, who is an alternative costume.
-Wolf, Snake and Lucas are cut
-Ganondorf has been changed a lot. The only moves he keeps are Flame Choke, his side tilt, and his air attacks.
-Falco is also further away from being a Fox clone.
-Corneria, Temple, Hyrule Castle, Fourside, Delfino Plaza, Poke Floats, Summit and WarioWare Inc, are the returning stages I know of.
That is all I know. (note: this is a throwaway account)