Top 10. Full uninterrupted season. At least one slam Semi. One Masters title.
I'm probably being incredibly biased as a fan of his, but this is as sensible as I can get with predicting Kei.
Full uninterrupted season would be awesome, that's what I most want from Kei. If that happens, no doubt he can make huge strides in his game, results and ranking. Once he gets into the top 12, he will be able to do a lot of damage in draws since there'll be a 75% chance his projected R16 opponent will be either Ferrer, Berdych or Tsonga, who he likes playing against and never lost to at Slams or mandatory M1000 (overall 2-0 vs Jo, 3-1 vs Tomas, 2-1 vs Ferrer, 2-0 at Slams overall).
Slam semi and Masters title might be too big a breakthrough for 2013, but hardly impossible.