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.