I think the below image is self explanatory...
Yeah, by comparing both of those the size looks almost exactly the same as the current Mac Mini. I bet it even has the same white plastic on the top.
I hope this is just a prototype and is not the real thing. I wouldn't buy it if it was the same size and has that same old awful white plastic. Apple needs to make it looking more like the Apple TV, which I think is all aluminum, but with a disk drive.