As we speak, the Apple TV is being marketed using phrases such as these (emphasis added by me):
"Apps have liberated television. They allow you to make individual choices about what you want to watch. And when and where you want to watch it."
It doesn't exactly scream "only content curated by Apple and its partners" or "only at home, not in your cabin". Note that the Apple TV already has some of the attributes of a semi-portable device. It already fits nicely in any kind of bag. It already lacks any sharp foot long spikes that would make it difficult to carry. Reading media files from a similarly portable USB storage can be seen as a very logical way to realize the promise of the quote.
I'm sorry did Apple forget to idiot proof that "where" remark with an asterisk?
And say:
"only where broadband connection is available" "where referees to anywhere in your home. As long as a LAN or wireless broadband is available" "Not meant to convey the Apple TV is a portable device"