Warning: Spoiler! (Click to show)
Part of why I think this is due to Skylar's comment you mention. The more I think about it, the more I say Walt triumphs over all the human threats...and loses at the very end to cancer. I could even see Walt standing victorious on the field of battle he uses that big gun for...then quick cut to him in a hospital bed, tubes galore, and you hear his tele monitor flatline.