It will depend a lot of his draws.
This. Purely based on the way he and everyone else played, he could have gone as far as the QF at the Australian Open with the right draw. Alternatively he could have got an even worse draw than he did and been knocked out in R1. All in all, R3 is a solid result for him and a good start to the year.
He's currently ranked 43. His first goal needs to be top 30 by Wimbledon, so he's guaranteed a seed on his best surface. His results on clay last year weren't amazing, but given it's his worst surface he probably shouldn't be counting on doing much more than defending his total there. Therefore a lot will depend on how he performs in the Spring US Hardcourts. Last year he had the following results:
Delray Beach: QF
Indian Wells: R1
That's a ton of points just begging to be picked up.
If he can be seeded by Wimbledon, then he should make at least R3 there and with a little luck can maybe go a little further. R3+ at Wimbledon means his ranking will get another boost and his draws for the rest of the year will look a hell of a lot better. Once he is regularly getting seeds into hardcourt tournaments there is no reason why he can't make some big inroads with his results.
If he doesn't get good results between now and the end of March, I think he is going to have a pretty tough year. He can still have a good 2013 but he will need to play really well and get a fair bit of luck with the draws at the big events.