Touch is one aspect, along with gesture and voice. All three go together to form the NUI, or Natural User Interface. Now THAT, is the future.
With the Leap Motion, you don't need to waving your arms around as you can do some small gestures as it recognizes finer input like that.
And no, a touch PC doesn't give you "gorilla arm." You have to be either REALLY misinformed, or doing it SERIOUSLY wrong. You can't take a non-touch set up and think a touch set up will work like that. It doesn't. You have to use a different setup that needs you to be closer to the screen, like if you were at a desk and using a laptop normally.
Voice control is already there, it needs refinement. In Windows for example, there has been voice control of the WHOLE UI versus a search box. Voice control of the UI and dictation is rather legit to use and is surprisingly good on a typical laptop mic.
I have to say about the gorilla arm thing again with touch, tell the elderly that enjoy using touchscreens and ipads because using a computer mouse aggravates their arthritis and tell that to growing section of society that is getting arthritis due to constant typing, texting, and mouse usage.