The Stick seems like a possibility in the next 10 years or so, but obviously must sexier than that render, hopefully bigger too. The Nano looks retarded and would be a massive step backwards. Tiny, none colour screen? May as well be a shuffle. Also no FF and RWD buttons? wtf? I don't even know what that last one is meant to be. Extra long iDevice? Offspring of iPhone and iPad?
Those are old. The last pic there is an Intel Moorestown prototype from 2007. That particular thing never got designed -- which is fine by me, as it was a ridiculous form factor.
The iStick looks more like an iPad alternative to me. Make it the same size and design some uber-gay looking belt holsters and ta-daa.
What in the heck does it do though? Also I answered your question, in regards to the stick at least... the only really viable one =D