I don't think it will have media center in it, that's on the way out but saying that I wouldn't be surprised if they market it as the Xbox Media Center. If it's about media first and some light gaming on the side then it's fine. And they've been known to reuse names from time to time. I also agree that this could very well signal the end of media apps behind Gold, which could also play into why it's been delayed as well.
We know they have plans to re-add features from their original XB1 idea but tweaked a bit, like family sharing and so on. Once they can add these more gamer specific features to Gold then keeping media apps behind Gold isn't needed because they've had been replaced by something else. The incentive to get Gold is still there, and maybe even better now with game specific things compared to media apps that more gamers should sign up for it compared to the 360.
As for the new model, if it's sold through the cable providers as a set-top box option it will be a success and it will introduce even more homes to Xbox and might get some to buy the full XB1 to get more gaming.