In the last chapter 646, we see Shunsui in a dire situation when he did not expect Lille Barro's transformation. Kaleo had the summary.
"After stating that he is the man closest to becoming a God, Lille Barro's eye begins to shine and a transformation ensues. This form resembles that of an angel, with eight wings protruding out of his body. On each of Lille's wings are three holes, which have the ability to fire instantaneous shots that obliterate anything it targets. Shunsui learns this first hand, as he is shot three times by Lille Barro's new form. The chapter ends in despair as it seems like Shunsui is down for the count."
The last panel seems ominous, as this time, it's Shunsui caught by surprise. While it appears that he might have met certain death, it's unlikely that a major character will perish quickly, as Kaleo stated. They also mention that it's time to reveal Shunsui's Bankai, which "can cover a wide area, but for what it actually does is still a complete mystery."
There was uncertainty on whether Shunsui was hit, but the last panel had Shunsui reeling, so it there was no question at all. Mangahelpers weigh in on the possible ace up Shunsui's sleeve that will allow him to survive. There's only one way to counter god-like powers-and Shinsui's bankai could ward reality itself.
"SO! I'm imagining Shunsui's bankai will allow him to create his own game or rules, user Ninjabot said. "Hence the reason he saves it for when absolutely needed, because by learning his opponent's moves he can perfectly design a game where they haven't the slightest chance of winning. But, he gets one rule set per release of Bankai, and he doesn't wanna waste it on someone who'll reveal an ability later that could potentially screw his game up."
One of the keys is when Barro stated that "his eye would be open" the entire battle. It is presumed that there would be a loophole in that.