I'm still not convinced yet that it's a single core, but it's way too early to know any other specifics unless IMG releases more info about it.
There are obviously architectural efficiency increases amongst many other factors like possible higher frequencies possible under 28nm that one should count in.
Will it help with the size of the GPU/GPUs if it is a MP-configuration? IMHO no. So the comparison with the HD6470M (FLOPs, MPixel, die-area) is IMHO still valid.