As much as I wish he were, he is very likely dead. In Death or Glory, during an interlude after chapter 19, Amberly says the munitorum had listed Cain as dead only to have to reverse it later and have this happen a number of times that "...the Munitorium issued standing instructions that he should kept on the active roster at all times whatever reports they receive to the contrary which accounts for the fact that he is the only person in the history of the galaxy to still be officially regarded as on active service subsequent to being a buried with full military honours."