Looks like spoiler for the next chapter is out:
Spoiler for Chapter 419:
It's official now, Aizen has trancended from a Pokemon into a Digimon with yet another transformation
. This time his face becomes different, his sword fuses with his arm, three holes open vertically on his body, and his wings become thicker with what looks like hollow masks at the edges based on the description.
Chapter ends with Ichigo planning to use the FGT on Aizenmon.