With the evidence that's been presented so far, it seems to imply that Gran Turismo has started moving away from the Playstation 3 and on towards the Playstation 4. That doesn't mean to say PD with stop updating GT6, as the two new VGT cars are bound to feature in the next update. Then again, I get the feeling that the VGT project will transition over to GT7, since more and more manufacturers are showing interest.
The Vision Gran Turismo project, above all else, is a stimulant for the internet. It captures the minds of people beyond just the Gran Turismo 6 players. Concept cars in general go a long way. Therefore, with GT7 on the way, now would be a logical time to make the transition in terms of marketing. It makes people think of Gran Turismo as a general franchise, rather than a specific game. The image is stronger in that way.
It's very interesting that these trailers and screenshots are hinting towards PS4 technology. Of course, it's mostly pre-rendered, but there is nonetheless a distinct difference between the previous VGT trailers and Bugatti's one.
I'm willing to bet that including the DS4 controller was done on purpose. If Sony is wanting Gran Turismo to step up its game, they are almost certainly considering us here on GTPlanet. It's just a way of keeping us speculating for the time being.
I wonder if they will show anything at Playstation Experience in December....