You can get very good body language through, but... it will cost you quite a bit in additional hardware (trackers and add-ons). The demand is clearly there and the supply is catching up (various competitors). I think competition will drive down the cost.

Audio is likewise a matter of cost. And manufacturers not cheaping out on components, I'm looking at you HTC (and the notoriously horrible Rift S too).

I'm looking forward to programmable smells based on a combination of basic smell cartridges. That's totally a thing people are working on.

Touch is a hell of a lot harder to solve. More could be done to provide good haptic feedback. Haptic vests and facial interfaces already exist (at additional cost, of course), but the problem is the more crap you have to add to your body the more inconvenient (and sweaty) VR gets. I believe providing better VR touch interfaces is key to the development of the technology.

And I really, really don't want to taste anything in VR!