A: He is dead because he hasn't been relevant to the plot since Madara showed up, or
B: He is alive for some unknown reason due to the Hachibi slashing off one of his own tentacles.
Until Kishi tells us for sure, there's no reason to speculate as there are really only 2 ways this could go.
His spiritual bond with gyuuki and him being pretty much the perfect jinchuriki could see him survive in the bijuus inner realm to be revived at some point so I'd say it is a possibility.