We recently got a new character and so I am with Bill Music or special moves or even another stage.
Perhaps it will be music that hints on a new character reveal.
If it is a stage, I predict it will be a stage that doesn't hint at any new characters. Perhaps the Mario Kart stage? Or I could see a cool Luigi's Mansion stage.
If it is Special moves perhaps MetaKnight since we haven't seen him in awhile. Or perhaps Bowser?
As for the Pitfall, I think this item is awesome. It is another in a list of strategy items, and not just weapon items. These are important, because they add spice and depth to gameplay without being a cheesy gun or melee weapon.
Also this will be a brilliant power to use against several different attacks.
Hammer or invincible star. Even someone about to start a Final Smash could be hurt by this item. It is quite fantastic.