I believe Porsche is in a very big dilemma..
If lets say it has ready the PDK gearbox and place it on the GT2, I believe that noone is going to buy anymore for psychological reasons 997tt. (Also cant place it SO SOON in 997tt as well)..
The problem though is that most of its customers (Who will decide not to buy the new 997tt) are not going to buy 997 GT2 either, as they wont have the driving skills or they may want a more everyday car. So they will definetely buy as a first choice Gallardo cars (I believe Gallardo is the step between Porsche and Ferrari) or as second option F430s..
On the other hand if lets say is not ready to place on 997 GT2 the PDK gearbox, it wont sell many cars.. As GT2 is a special car for enthusiast drivers who know exactly what is going on with the new technology...