Murray is currently 2055 ranking points back in "Race" points. He is currently scheduled to play all of the tournaments on Nole's schedule through the year's end (Shanghai, Paris, London) plus Beijing and Vienna- both 500 level tournaments. Even if Murray wins both 500s (which is certainly possible), he would have to outperform Djoko by 1055 points at the other three. I don't foresee that happening... but who knows.
I think a more likely spot for him to overtake Djoko (if that were to occur) is between the AO and RG next year, as Djoko is defending a ton of points compared to Murray in that period. But even then... Djoko is defending those points for a reason.