Okay, reading last week's chapter, I was leaning towards Sabo being alive…but I read this one and now I think Sabo may be dead after all...here's the reason; if he was taken by the Tenryuubito, wouldn't Ace have found him by now? Ace doesn't really hit me as the sort of person who would back down just because his enemies are dangerous. But Ace seemed to be living his life completely free of the burden of searching for a kidnapped friend. I just think that had Sabo been alive as a slave, Ace would've either found him, OR asked Luffy to find him before he died.
Another thing, if Sabo died and the last thing he said to Ace was "Get over your death wish...LIVE!!", that would completely justify what Ace said before he died "If it wasn't for you [Luffy] and that whole Sabo thing"
I just think that Sabo dying at this point would definitely give Ace a reason to want to live…for his sake!