ADias:
VW may consider the A8 better from its modularity/component sharing perspective. But that does not make it a better platform for the consumer.
Big companies need to earn money. Period.
Better platform for the consumer ? Well...the A8 platform also has its advantages, it allows Porsche to always use the latest technology (navigation, night vision, gearboxes, drivetrain, etc. etc.) without the need to actually develop it completely new. It is easier to adapt technology to needs than to develop it from scratch.
Btw: the A8 platform has its compromises (of course, it needs to "fit" different cars) but it is actually a very good platform as far as I heard. The development cost was around 1.5 Billion EUR, the development cost of the Panamera platform was 1 Billion EUR. Porsche needed to do a lot of things from scratch, VW/Audi profited from former experience.
Look at the current Cayenne: most of the blackboxes, drivertrain, etc. actually have the VW logo on them.
It doesn't need to be a bad thing.
Porsches are getting more and more expensive, lowering production cost will allow them to keep their current price level or to offer MORE (options, etc.) for the same money but at the same time allowing them to be very profitable.
I don't think that the "regular" Porsche customer will ever know/learn the difference. Not everybody is a car nut like WE are. 
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RC (Germany) - Rennteam Editor 997 Turbo, BMW X5 M (03/2010), BMW M3 Cab DKG, Mini Cooper S JCW