I think Super smash Bros 4 should include all the characters from Super Smash Bros Brawl. Though I believe we should get rid of Toon Link. The other combos are okay, as it balances it out. Now, below are a list of (in my opinion), characters that should appear in the upcoming game:
Bomberman - Perhaps, he could have strong bomb attacks and moveset similar to Luigi. He could be a light and fast character. His final smash could be a multitude of explosions
Megaman - I strongly believe Megaman should appear. He could be a heavy character who is sort of slow, like Bowser. But his attacks could rely much on his blaster. his moveset can be similar to Fox or another character with good punching abilities. Rush could make a brief appearance as part of his moveset.
Tails, Knuckles, or Shadow - I strongly believe one of these characters should make an appearance. I think they have great potential as characters
Birdo - Maybe.....just maybe. Probably not.
Bowser Jr. - Probably, but maybe not. I mean, he has some potential.
Hammer Bro - Sure! That sounds pretty good to me! Strong hammer-based attacks
Koopa Troopa or Koopa Paratroopa - Doesn't have as much potential as Hammer Bro for attacks, but I think that would be cool!
Daisy - Sure! She could have a similar moveset to Peach!
Lakitu - Maybe, he has some potential, but since he's in a cloud, not really....no
Little Mac - Yeah! He should be in it! A good arsenal of boxing moves and quick agility sounds really cool!
Kamek - The idea of Kamek using a powerful array of magic sounds like a good idea
Knuckle Joe - This just sounds really cool! Fantasy fighting moves based off of those in Kirby
Starfy - He could use some water attacks and spin attacks
Kat and Ana - They could fight together like the Ice Climbers. You could control Kat (or Ana) and the other in the duo will be controlled by the computer and fight with you. They could use ninja-based attacks and katana attacks.
We have Pokemon Trainer, Pikachu, Jigglypuff, and Lucario running around. But there are over 500 Pokemon in existence, and some incredible ones too. We should keep the first 4 mentioned above. But I'd love to see some Pokemon like Magmar, Alakazam, Gengar, Typhlosion, and Weavile thrown into the mix.
That's all for now, but I'll think of some more later!