Not sure if it's been confirmed elsewhere, but if it has I haven't seen it. I've just seen a gt6 case in game which confirmed Brands Hatch will be in GT6! Great news!
That was from the initial Silverstone launch but many of us questioned if it was real. A couple of people from here then, like you, saw the same thing in GAME seemingly confirming it was true.
I remember driving brands ever since the first Toca came out. I love that circuit. I like the short version best, because it's well, short. The long version is nice to.