If you look at the images on AutoBlog, you will see that the scoop is basically taped on the hood. I think they are testing drivetrain in the shell of the Impreza.
testing impreza drivetrain in impreza shell? i can almost guarantee you it will look nearly exactly like that. haven't seen a car with spy photos this numerous on the interwebs be completely different. besides this would follow their current line of aesthetic reasoning
If you read the article found at the link you will see that they are planning on making the wrx/STI a distinct model differing from the Impreza(as it is now).
Definitely not the upcoming WRX since that would go against everything Subaru said about making the Impreza less expensive by turning the WRX/STi into distinct models, allowing them to engineer a small consumer car without having to take those performance aspects in mind that they've had to in the past.
creating a completely different platform is NOT, nor will it EVER be cheaper. so not sure how they figure it will lower the price of either chassis. hence why Ford and Chevy are going to global chassis (same cars available in Europe available here, just not the same add-ons/etc)