User blog comment:LucariOP/Smash 5 Speculation/@comment-25476555-20141113193054/@comment-15197626-20141116191733

So far, all pokemon reps have stayed beside Pokemon Trainer, who was cut because of hardware limitations, and Pichu, who was PROBABLY cut because he was a COMPLETE Pikachu clone. And, since Greninja isn't a pokemon that switches between pokemon, and isn't a clone, he has a pretty fair chance of staying.