I don't think there is a good way of telling from the present vantage point. Will Roddick call it a career after a couple more seasons, or will he be more like a Connors or Agassi and keep going strong deep into his 30s?
I've heard him talk as though he doesn't plan to keep going long past 30- if we're looking at retirement at, say, age 31, then he will likely have difficulty compiling the necessary 10 additional titles within a mere two-and-half year window. On the other hand, I do think that he is a guy with the potential to keep himself relevant past the age that most players could; if he stays on tour for another five or six years while retaining his serving arm and fighting spirit, then I don't see why he shouldn't be capable of remaining at least close to the top 10 and getting himself up into the 40-career-title range.