No.
Well, alright, maybe. But web download would surely be the way? Why would a software vending machine be immune to all the vending machine problems. Bubblegum in the firewire port? I've heard speculation of the same for broadband download - watch your movie and then it corrupts after a few days or whatever - you never even leave the house. Sorry, its just I like your idea of not having to go back to return the disc - but why go to pick it up?
'But not everyone has broadband' you say - but this is only a matter of time, surely, as increased DSL (or the next technology) speeds become cheaper and more widely served. The kind of people who have an iPod (or your alleged iBox) probably have broadband - I don't see them producing a line of vending machines just to cater to that section of the market that have an iBox (or nearest comptetitor Sony Videoman, or Hitachi Portable Media HD or similar that will come out) but don't have broadband.
Surely they'll do away with stores altogether eventually, and the vending machines will just be for Cletus to take the disc to play on his WWF-branded all-in-one Sanyo Media Center back at the trailer park because he's on the wrong side of the digital dee-vide....
In the future, we'll be fibre-optic'ed up the ying-yang and things like mobile phones and flatscreens will be disposable....
Anyway, its all speculation, as I'll believe this iBox when I see it....