The rumor comes from the latest Zune newsletter that posts a link to this survey. After click "Yes" to the first question, question number two asks "Have you ever connected your Zune to your Xbox to do any of the following?" Not newsworthy, except for the fact that one of the possible answers is "Use my Zune hard drive for extra Xbox storage". Interesting ...
Just don't get too excited, because survey answer could have duel meanings. It could be referring to a Zune being used as official Xbox 360 storage allowing game saves and Marketplace downloads, which would be BIG news. Or the survey answer could be referring to the Zune being a portable media device and used as music and picture storage for use on the 360. If that's the case, this isn't news.