Behold... the 2008 Chevy Impala-- or at least, that's what The Car Connection thinks it is. The mystery vehicle in question sports round rear taillights, a grillw that looks suspiciously like the 2003 Chevy SS concept, and a long wheelbase. TCC makes a good case that the prototype is rear-wheel drive based on its similarity to the Zeta-based Holden Commodore that spy photographers shot tearing around GM's practice tracks. All of this follows the now-conventional wisdom that GM will swap driveline ends with the Impala, which in recent guises has been suffering the ill effects of torque-steer due to massive power increases.
Of course, it helps that with the increasingly common use of technologies like traction control and improved snow tires, rear-wheel drive has once again come into vogue (read: "Thanks, Chrysler 300!").
[Source: The Car Connection]