I'm sure there are many features that still need to happen. I'm sure there are developments yet to be made. But aside from obvious pie in the sky pure sci-fi lunacy like motion capture for VR or augmented reality applications, I can't think of anything that's even remotely attainable.
Bright display; Durable; simple usability; "interface feel" extremely satisfying; the freaking watch dial rotates how cool is that
not enough apps; so much utility potential as yet untapped..