Yes, clearly that was always the plan. However, it isn't very subtle or believable, and it feels cheap, hence what I said about the show coming up against the limitations of Gilligan.
The transition:
Season 1 - He doesn't really do anything wrong, unless you consider cooking meth to be wrong in and of itself.
Season 2 - He lets Jane die. Kind of a dick move, but it's understandable.
Season 3 - He has Jesse kill Gale at the end. Justifiable. Before that, he's basically the same guy. Skyler forces him out of the house without the slightest opportunity to talk things through and later fucks Ted, so we really sympathize with Walt throughout this season. Heisenberg started to grow more dominant in the I.F.T. moment, IMO. Up to that point, he had done quite well at balancing the drug business with his family life, fugue episode aside. With his wife hating him irrationally (the writers' fault) and fucking a man like Ted, Walt starts to give less of a fuck.
Season 4 - He gives Brock a shitty weekend in the hospital and sets up a situation where anyone walking by a particular door in a nursing home at a particular moment in time would probably be injured. And he tricks some old lady into doing his recon work for him. He's becoming more of a dick, but at the same time, he keeps his family safe and takes out a major kingpin. Skyler is even warm and tender with him at certain points. Things seem to be heading for a reconciliation and happy ending, until...
Season 5 - Walt is a dick to everyone and isn't bothered when a kid gets shot right in front of him. In an unrelated turn of events, Skyler treats him like he just sacrificed a baby in front of her. The subtleties their relationship had in Season 4? Gone. We're back to Season 3 black and white irrationality.
The show is still great, but Season 5 Walt doesn't really feel earned at all. I'm still fascinated because Cranston is that awesome of an actor.