Last time we saw him, in Owari, Mikey demutated him back into a human, and he punched him in the face for being ungrateful, and we just saw him lying there unconscious on the ground. Then the building was on fire, and after Leo finished Super Shredder, the building burned down, and we never saw Stockman escape. At one hand, he could be dead because he was the only one of Shredder's hench men that didn't appear in Season 5, but on the other, Fishface's legs and water breathing rig (which might I remind you that they were detached by Raph) were fixed and Stockman was the one who built them, so...
'IS HE OR IS HE NOT DEAD!?!'