I'm pretty sure windows ink support, materials and kickstand.
Also i think is not enough for stand out and so i hope for something really new...
Pretouch, physical keyboard or double screen using hinge(like surfacebook), eye control, flexible screen, integrated/module projector(for continuum), a dumb tablet in which you can insert the phone like asus padphone, cover with second screen, something related to windows holographic, some way to run win32 apps through cloud or emulator.
I know these things are very unlikely(some are only my hope, some come from rumors and Microsoft research videos) but they NEED to do something really different for gain market share.
I hope they will surprise us!