1) Either wait till 2013.
2) A car purchased in (even in) March/April/May etc 2013 can also be a old stock car and reinvoiced as a 2013.
3) Their was a red coure on sale on Pakwheels registered in 2009, but the model was 2010 (as per the motor registration website karachi).
4) The car sells on its condition, the model shouldnt have much impact., If the dealer offers you some year end discount on that car its a good option, as of 1st January, gariyan bhee short hojaingy, demand ber jaigy, price ber jaigy bla bla (dealer tactics)
5) Discuss the mater with the dealer, they would tell you, sir apko issi gari ki invoice 2013 ki banwadeinge, But the registration and invoice both should be of 2013, Or else the conflict in the above Coure case is obvius that the car was either reinvoiced or (dramei bazi) or else how can a 2010 model be registered in 2009