GT3 is about homologation for actual racing. PDK is faster. computer-controlled automated gearboxes came from racing like F1.
The GT3 and GT2 are migrating to the M97 derived engines, rather than Metzger blocks, to fit the PDK gearbox.
And even if they do have manual gearboxes as an option, an ultra over-drive is rather pointless on a race car homologation... a 6MT would probably be fine.
991 is out... I want to see the 981 Cayman next... but that is rumored to be held back until November, but I have no idea why... 981 Boxster is already out.