Last we saw of Hisagi was Tousen's death scene; he may be gone forever, for all I know! And Yoruichi's been gone since around chapter 200, which was... oh, god, we're at chapter 396 now, so that's just one month from being half the series ago. This arc has been going on for that long.

I guess that she'll show up whenever Urahara does? Maybe? She'll probably be in a refrigerator.