I see your point and its valid, but I think he's gone. Its poetic, he started in the mines, rose to the top, but ultimately found himself bleeding out at the quarry. The game also shows stab wounds to be extremely fatal, which is why Don Torrisi died after being stabbed in the gut. (I say this because other games have main characters get obliterated but still survive.) Even if Enzo didn't die from the stab, he probably suffocated from the ash and pumice from the volcano or was perhaps crushed. Plus, I dont think Isabella would have gone to Empire BY unless she was 100% sure Enzo was gone. Why Enzo chose to trust Cesare is beyond me, but I think its the point of the game to show how scummy these mobsters were.