Personally, speaking as an ex smoker, I would be a little frightened of WDW if they went totally non smoking. I agree that the designated areas need to be better enforced, but unlike a bar or nightclub, you can not just step outside to have a cigarette. I know that I became pretty testy after a few hours (and for me it wasn't so much nicotine as the oral/manual thing, so nicorette wouldn't help) and the last thing I want is to be waiting 90 minutes for Fantasmic next to a group of smokers who haven't had a smoke for 8 hours. When I did smoke at WDW, all those years ago (ok, 4) I stuck to the designated areas and really only went to smoke after I considered strangling a woman with her own backpack after it hit me for the 5th time. I don't think smoking will ever be illegal, but I think we'll hit a time when most people just "wise up" and don't start in the first place.
And, also speaking of as an exsmoker, most smokers out there know they're addicted, and they want to quit, but the feeling of defeatism is so strong, mixed with a feeling of guilt, it's a tough, tough road to walk. I actually used a drug counsellor to quit. He said quitting cigarettes was harder for him than quitting hard drugs. If you want to encourage people to quit, don't use a scare tactic (we know em all anyway) but positive support. I promise you, there's not a single smoker out there (ok, maybe a few crazy ones) who is going to say "I'm giving your kid asthma? Great!" but attacking smokers just gives them reason to feel a need to band together, and even a reason to keep smoking.