Boxster Coupe GTS:
Porsche actually did conduct a detailed survey of existing GT3 and GT3 RS customers.

Of their existing GT3 and GT3 RS customers, they found that 100% or respondents drive with a manual transmission.

Apparently the existing GT3 customer base enjoy the interaction of changing gear as part of the driving experience, spending time to perfect their heel-n-toe shifts and throttle blips to let that Mezger engine sing!
That is not to say that some or many would not enjoy the interaction of changing gear using paddles as part of the driving experience and letting the new engine spin to 9,000rpm etc

Boxster Coupe GTS:
The GT3 developed a reputation of feeling truly outstanding to drive at any speed, on road or track. It was clearly the definitive established benchmark for owners and competitors.

It is clear that the 991 GT3 was not designed with existing GT3 customers as the primary target.
That is not clear at all, just a sweeping generalisation.   It is likely to appeal to many existing GT3 owners (and some owners who haven't previously owned a GT3 for whatever reason).  Of course there are some existing owners that won't be interested in the new car.

Boxster Coupe GTS:
Indeed, for existing GT3 owners the 997 GT3 RS 4.0 is a far more attractive proposition.
Again, another sweeping generalisation - for some owners that will be the case, but you simply can't generalise like that, not least because the 991 GT3 RS is the direct comparator, not the 991 GT3'

Boxster Coupe GTS:
For 997 model PDK drivers, or drivers from other marques, the new 991 GT3 will be an amazing car.
And for many existing owners who are open to new technology and who appreciate the difference between the PDK-S gearbox and the traditional slick box automatic!
Boxster Coupe GTS:
However, many existing GT3 owners are understandably looking forward to the announcement of the Porsche 991 GT3 RS...

Whether they will buy one is a different matter.

Put simply, the GT3 is a road car capable of excelling on the track.  The GT3 RS is more of track car capable of being used on the road.