There are some minor ui elements incorporated in Media Center (Win7), XBox NXE and WM6.5 ui. But what I think is about to finally happen...is a unified marketplace. I get the feeling that "XBox Live Video Marketplace" will be incorporated into and renamed to "Zune". That would be a welcome change in branding. But I also think they are re-engineering this unified marketplace to be based on Silverlight/Live Mesh App so it can be offered via web portal, tv (via extenders & media center & xbox), phones, etc. Hopefully this will support both streaming and download options.
Further, I would be pleasantly surprised if we saw a Zune branded Media Center Extender this year. I've argued in the past that Zune's AV dock should be a low-cost/non-gaming Media Center Extender. We'll have to see what happens on this front.
Windows 7 - Gateway Laptop, Windows 7- Gateway Desktop - Dual 22" LCD
Windows 7 Media Center - HTPC homebrew, Dual Tuner
XBox 360, Zune 120 and Windows Home Server - HP MediaSmart (3 TB)