Murray is taking the first step towards achieving his first number #1 ranking. He reached his career high regarding ranking points (8480 now, 9280 if he wins AO).
he had 8570 points after the US Open, will only do better if he wins the tournament.
And even if he wins the tournament, he will not do better than his best with the old ranking system (5505 points on the 24th of august 2009) : at the moment he would have 4950 points with the old ranking system, 5250 points if he wins the tournament. Hasn't done well enough in Masters 1000 tournaments comparing to what he did in that time (he held 3 Masters 1000 tournaments at this moment, and even 4 ones before Cincy 2009)