I guess the inevitability of his death does cheapen his final plan for me. He gets a free pass because he knows that, as always, he doesn't have to pay for the consequences of his actions. So the fact that he can end everything (or at least, quite a bit) on his own terms, while hardly redemption, seems a fate far too kind for Walt.
Why does it cheapen it? He's a bad person, who's selfish and does bad things. Bad people don't have to always face the consequences. I don't get why people feel this HAS to happen in literature. I get why people want this to happen in real life, because - well, we like to think bad people don't always get away. But you know, sometimes they do. And I would reckon that, bad people don't always feel bad for what they do either (which is how Walt went out, feeling good about it).