At SEMA, the hint was dropped to look for improved new content, not just more GT-Rs. The C7 Vette may be part of that, but the real C7 won't be released until next year, so who knows just when we will get it. They released a video about the new NSX in January, but we still don't have that car.
The video camera used to make this video probably is nothing special and it's mic is clipping a lot, but it just goes to show that what PD uses in GT is not based a lot on the real sounds. Just changing to the 6-speed transmission will completely change how any car sounds in-game because they figure that all 6-speed transmissions have screaming square-cut gears and its sound takes precedence over any engine sound. Trying to do too much in the wrong way?