The way Kubo wrote those chapters, yes I thought Byakuya was going to die. I think Kubo tried to kill him but in the end couldn't do it. That or fangirls threatening to kill themselves (it has happened before) or threatening to stop buying Bleach.
Manga authors are usually several chapters ahead of the chapter currently being published. By the time that chapter was out and fangirls baying for his blood, Kubo would have been many weeks worth of chapters beyond that point. So, I very much doubt the 'fangirl effect' was why Byakuya survived.
With the way recent chapters have been unfolding, Byakuya's situation actually fits in with a theme that's visibly unfolding which hasn't yet been truly explained - the impact of taint. It was emphasised to painfully obvious extremes that Byakuya's injuries were blighted by taint and he only stood a chance of recovery if the taint could be completely purged from his systems. That was, in fact, the reason for the healing method Kirinji was using on him: he had to be purged so utterly of that taint that he was practically being rebuilt.
Only after this extreme story line occurs are we given the Isshin flashback - and the major issue that comes out of that part of the flashback is the importance, the problem, of taint.
It is beginning to feel as though Byakuya's injuries were caused for a reason... not only the method by which he was so badly injured (which itself is part of an ongoing theme: the warrior instinct, and Byakuya's own value on it) but the using of his extreme injuries to heavily emphasise the problem with taint.