I see on the SA site that it should be available, the Time Warner site doesn't mention multi-room ability one way or the other, which leads me to believe it's not yet available... I could call them but I doubt I would speak to anyone who knows what they are talking about.
I've had an Explorer 8000 for over a year and it works great. I just bought a house and have been running the RG6 cable while I have my walls and basement ceiling all open... I'm wondering if I should run a 2nd line of RG6 cable to each room to "broadcast" the exisitng Explorer 8000 or 8300 signal to my other TV's or if the Multi-room box is out (or will be any day now).