Definitely something we're looking at especially in respect to tablets. Mostly focused on video capture from the phone and playback on the tablet although we would not artificially restrain the experience as such. Not ready to share timing yet but am happy to hear more about how video would be used in your communities while mobile.
By the way, externally hosted videos that are embedded in content (such as YouTube) do play back nicely in Jive Mobile already. The constraint is with the Jive-delivered video.