Board Thread:General Discussion/@comment-1351982-20131110213812/@comment-8986886-20131110231846

Ukitake will be slain by Haschwalth. This will cause Shunsui to avenge his old friend, reveal his Bankai and completely destroy Haschwalth in an epic battle.

(Edit: As to why Ukitake will be matched against Haschwalth, he can be considered as second-in-command, by seniority, just like Haschwalth is second to Yhwach among the Stern Ritter; and I believe Yhwach still thinks of him as number two, despite Uryu's nomination.)