Genesect will be 4th new pokemon character in smash.
sorry to jizz all over the hype train ,but...
1. weak to fire/good against dark: balances type effectiveness against charizard and greninja
2. represents black/white era
3. starred in movie 2013
4. ultimate "villain" pokemon character (mewtwo used to be but no more)

all pokemon characters represented in smash 4:
-jigglypuff (super lightweight)
-pikachu (lightweight)
-lucario (medium weight)
-charzard (heavy/light weight)
-genesect (heavyweight)

pokemon trainer for use as OPTIONAL rotor system with pokemon of choice
possible 6th pokemon character to stay true to series

I don't believe mewtwo will return