User blog comment:Skitzo1/Anyone else hoping for a Unohana flashback to see her bankai?/@comment-6904925-20130608192738

Personally in my opinion, I don't think she's 100% dead, I believe when she said she was dying, she was just dying as "Yachiru" and so she can live as "Retsu'.

Or perhaps Kubos got another surprise waiting for us

(My own theory)