Not so much "new" as "custom"/"proprietary". Apple designed and makes these cards not AMD. Apple has licensed some stuff and buys a few basic components from AMD but it Apple's card.
It will show up once macrumors and other rumors sites get indexed.
roughly
D300 approximately a W7000 ( less VRAM 2 versus 4 ) [ approximately AMD HD 7870 ]
D500 approximately a W8000 ( less VRAM and fewer cores and tweaked memory width ) [ approximatel AMD HD 7950 or AMD HD 7870 XT ]
D700 approximately a W9000 [ approximately AMD HD 7970 ]
Actually D700 has a lot more power than HD 7970 according to the specs.