Even if the marketing deal with Ford hasn't lapsed, they don't own Aston or Jaguar anymore (I think it's plausible that the deal for Quantum of Solace was done before the sale of Aston was finalized). Prodrive will probably want to negotiate to get another Aston Martin in the film, but it may happen that some other company (BMW again? Mercedes?) steps in with a better offer.
But enough of business, what would I like him to drive? I think Aston Martin is the best choice, they combine superior performance with the high class image required of Bond. How boring would it be if he had to track SPECT... er, Quantum, to a cut-rate carnival in Delaware? No, the purpose of James Bond is to drive expensive cars to expensive places.
So, if not an Aston, a Ferrari would work, but all their current cars are ugly. Lamborghinis are too flashy, Porsches aren't flashy enough, Rolls Royces are too slow, Lotuses are too fast, and Jaguars, Audis, and BMWs are all too cheap (ha!). I'd like to see Bond in an SL65 Black, but it's too race car-like.
I think the Maserati GT would work, but I have some irrational bias against them.
So, I come to no surprising conclusion, Aston Martin works best.