Who's the new bad guy in New Super Mario Bros U?

[CM30]

Not the final boss (presumably Bowser), but who do you think will be the mini boss/minion/bosses fought in fortresses/towers/castles/airships?

So far we've had:

Original bosses and Bowser Jr: NSMB

Koopalings, Bowser Jr and Kamek: NSMB Wii

Boom Boom and Pom Pom: Mario 3D Land

Koopalings and Reznor: NSMB 2

Who's it going to be in this game?

 

[Dark Young Link]

I feel like it'll be Bowser Jr. since he's a staple of the NSMB series and original bosses. I want the Koopalings, but there's a small chance. I'm willing to bet that Kamek will be there too.

 

[Gelivable]

Mario 64-styled bosses maybe?

 

[Darking]

I'm hoping to see new enemies, a la NSMB, but with some classic ones, like King Boo, Gooper Blooper and Petey.
And who knows, maybe Metal Mario appears also as a boss. I would love that.

 

[Super Leaf]

I hope it's Boom Boom and original Bosses