Ichigo's bankai is different as it reaches new power growths. It is still young, BUT his bankai so far has been the reflection of his inner hollow. Its colors are completely inverted compared to a normal Zanpakuto, black blade instead of a silver/steel like everyone elses. As we saw the Black Hollow "White", fighting Isshin and Masaki, its blade arms are exactly the shape of Ichigo's current stage Bankai when he received his new Shinigami powers to fight Ginjo. Which brings us to Ichigo choosing his Assauchi, or rather i believe his Assauchi chose him and showed him what he fears most is his greatest weapon... his inner hollow.
Imo, either Ichigo will get a similar Zanpakuto but with another set of powers. But i really think he will get 2 zanpakutos, both shorter blades, not much smaller, but quite similar. He will be dual wielding them.