well yeah his Zanpaktou(soul slayer) was there(in him), but as of now if he did know what was up, then whoever killed him(Im betting on Gin) did it at the PERFECT time. just looked at it this way:
1. We have Intruders here that are causing a commotion
2. SS is in chaos
3 and whoever was doing something(if there is a conspiracy) just found the perfect oppurtunity to do it. So leaving it there made it seem like he wanted to(on purpose)