No, there is no confirmation of that, also they stop calling him a corpse after this. If Toshiro had died after becoming a Zombie he would be resurrected and not be the mindless doll that he is. there is no confirmation that Toshiro died after becoming a zombie. Granted the wording could be taken a different way if you want to read it that way, but there is no confirmation yet, even I, who have no respect for Kubo anymore, can not believe that he would A) be stupid enough again to kill off one of his top five favorite characters and B) be stupid enough to give that character a death that that happened because he passed out.
Honestly, the very last thing in the world Kubo needs is to loose more readers and the death of a character so incredibly popular as Toshiro would loose him a large portion of fan base, just the angry and stupefied reaction on here proved that. Also, I'm not sure if it has anything to do with it, but there has been a huge lull in the posting in the Bleach section here since the last chapter.
Kubo was not stupid enough to kill off Byakuya and I seriously doubt he will kill of Toshiro, unless he is completely stupid and doesn't look at the popularity listings of his own characters.
Also Zombie doesn't always mean dead, being a Zombie can also mean being mindless, as Toshiro is. Honestly, there is no way of knowing yet, I'm still ready to dump Bleach at any given second if Kubo has finally nailed the lid shut on his once great creation.
Yes, reading back terms such as "before death" sound ominous, however, Kubo seems to be hinting at him not being dead, while saying he is at the same time, as before Bambi said a soul reaper does not need to be dead for her to control. I think this is Kubo's way of keeping the readers in suspense.