There's no hint of other villains.
I've also heard that there's the whole bringing in other Kryptonians (LAME). The only other Kryptonian I want to see is actually an Argosian, and that's Kara, aka Supergirl.
Superman's got enough villains without having to dip into the whole Kryptonian thing or using Kryptonite. They can use Brainiac, Metallo, Parasite, or Darkseid. Personally, I don't see Singer using any of them (or bringing Kara into things), and I think he'll probably go the Kryptonian angle because of Zod.
There are a couple of scenes like the Martha scene, throwing the continent in space, the crystals that were dropped by Kitty, and Lex's comment of the crystals taking on the properties of the minerals around them.