[Whewt22]

I guess, Aizens distrust in Gin is also supported by the constant tests he sets for Gin. Almost as if he doesn't trust him and sets forth tasks to prove his allegiance. Such as killing Rukia after he got the hougyoku.

There are also some hints at Gin fighting back, such as not killing Ichigo at the gates, or not stopping Ichigo as he passed by him to save Renji's life.
We'll see though...