New form factors -- keyboard, flip/clamshell.
Surprising internal specs -- storage, speed.
More screen changes seem unlikely though [1]. The density/resolution is already a huge, attention-grabbing update. Apple tends to parcel those updates out. E.g. they didn't jump straight into HD video capture. They released a slightly-better camera first.
New form factors strike me as about as likely as a convertible tablet MacBook or an attached-keyboard iPad update.
The internal specs... Apple doesn't talk about those much. Surely it'll be even-faster with more flash. But beyond confirmation of an Apple-designed SoC [2], they wouldn't even mention those specs. Let alone hype them to the press.
[1] Does PixelQi even have samples at the pixel-density the update is boasting? Let alone at volume? I honestly don't know.
[2] Something that would have been spoiled by handing the hardware to Gizmodo btw
OLED screen? Their competitors are already there and userland's reaction has been decidedly mixed.
I honestly can't think of anything else. Pony?