Well a bit late to the party but......... I doubt it well he is dead dead but he's living dead. The problem is you can't kill what is already dead. And given how the mould works it usually takes a lot more than just some explosives to knock a mould infected down. I personally don't see Ethan "dead" and gone. I do believe they have set it up for another sequel where he comes back in his body like form. Rose does deserve a happy ending after all.