This is not a new Porsche 928. It's just an interesting sketch, found posted on the internet at Porsche Consulting's website. There are some new rumors about a two-door GT in the same vein of the Porsche 928, and this sketch is similar to some of the renderings that have been floating around. Of course, you toss a bunch of Porsche design elements in a blender, and it wouldn't be hard to come up with this vehicle.
The takeaway here is that there are likely hundreds, even thousands of drawings floating about in Stuttgart that show cars with no true bearing on production reality. Despite rumors that Porsche is working on a new 928 that may be a Panamera variant, it'd be a stretch to believe that this sketch represents anything about that project, barring specific knowledge. If it helps you sleep at night, go ahead and ascribe undue importance to it, but until anyone knows more, remember that this is just a cool picture on a website. Thanks for the tip, Ian!
[Source: Porsche Consulting]