Dang, im hyped about this one.
After random babbling from Renji about Urahara's Bankai, im hoping for a release soon XD
Its gonna kick ass, purely because his Soul Slayer has the word Crimson in it.
Anywho, heres my idea what its going to be.
Starts raining blood (yeah, Slayer style \../), and Urahara can control and manipulate those blood-drops into spikes/swords/sheilds or whatever he wants.
Would be pretty cool, but i dunno, just my random guess, taking idea's from his Soul Slayer's name and Shikai.