Yes, you could turn your Xbox1 into an Extender for MCE2005 (and I think 2004). Xbox360s work with all versions of Media Center.I heard of Media Extenders for XBOX. Never saw one before. But I came across some news recently talking about beta version of Media Extenders.
But there were several third-party extenders that worked with versions of MC before Vista (Linksys had one, HP, etc). And the next generation of third party extenders, that work with Vista, were recently announced. Those are the ones in the article you linked, but I don't know why you would refer to them as beta devices. They aren't; they will be on the market for the holidays.
Pretty much everyone is copying Microsoft at this point. But if MS copies anything from LinuxMCE, I hope it isn't that UI. It makes my eyes bleed.Let's see how much Microsoft will copy these features (from LinuxMCE).