Board Thread:Questions and Answers/@comment-10797017-20130627100621/@comment-5657895-20130718030742

Yeah, but I just don't think Ichigo leaving Karakura town would be a good move. It doesn't suit him, the character that Kubo has developed for so long.

And Kubo drops characters in mid-build all the time. He does it constantly with Chad and he does it to Kira, Momo, Ukitake, Ginjou, and Orihime from time to time as well. He's never been the most consistent of writers, though I blame his editors. Maybe this thing with Karin will go somewhere, but her becoming a Shinigami doesn't seem likely, not unless Kubo makes some drastic changes come Blood War: Seperation time.