This is Hollywood we're talking about here. Sheen is hardly through. Look at Robert Downey Jr and Lindsay Lohan. They don't operate in the real world out there.
Both of them seem to at least be trying to get better. Sheen seems to be embracing his madness and going deeper into it. He's not sorry for anything he's done and seems to be actually proud of it. That doesn't spell "comeback" to me. That spells "checkout". As in, he ain't gonna be with us much longer.