Pure speculation, granted, but I've found this on the Samsung site whilst looking for a cable PVR picture. You may recall that Virgin earlier this year mentioned a new V+ box being available in the second half of 2008, initially thought to be another Scientific Atlanta box (like the current V+) but later confirmed as a new Samsung machine.
This is the cable PVR on Samsung's international site; 160gb drive and just two tuners, but with both Mpeg2 and Mpeg4. More details here. If this was the release spec (which I doubt) that's a more HD capable box that would probably benefit from a bigger disc. It's a nicer looking box to my eye, looking more like a regular domestic piece of kit than the somewhat space age and plasticky design of the current V+.
Then again, it could be a completely different Samsung box or it could even be that the Samsung V+ never makes it to Virgin customers as it's still in the labs at VM and there've been no official announcements.
