Each GM brand has always had their own vehicle. The last example of this was the Cadillac Fleetwood, Buick Roadmaster, Chevy Impala SS and Chevy Caprice. They were all basically the same car, all with the same drivetrain.
Ford and Mercury, Infinity and Nissan, Honda and Acura, CHRYSLER and DODGE, every manufacturer does this.
I for one can't wait until February. The only reason why I'm driving my Charger right now is because I couldn't get the dealer to come down any more on the asking price of their Caprice PPV.