I think Disney is getting the hint about non-smoking rooms and are alloting more non-smoking rooms in their resort.
I was at the Polynesian during Thanksgiving and had a non-smoking room, but noticed a burn mark on the table from a cigarette...Hmm, non-smoking room to that person MUST have meant no ashtrays!!
all in all, I only noticed a few people smoking (right outside the entrance to Captain Cook's. That makes sense... door opens, smoke goes IN the restaurant.
AND last but not least... EVEN with the announcements and signs that smoking is only allowed in designated areas and to ask a cast member for help, etc" only a few people were walking around Magic Kingdom smoking ...
Have you ever seen "A league of their own"? with Tom Hanks-- "THERE'S NO CRYING IN BASEBALL!!" Well, when I saw someone smoking in an area not designated as smoking, I would say in that same tone, "THERE'S NO SMOKING AT DISNEY!!" My daughter was ready to kill me, but that was nice compared to what I usually say to people!!! I know it's an addictive habit, I used to smoke, so I know what it's like, but I also know what it's like now not be be able to breathe when someone is smoking around me!!
So, to answer your question, don't worry, you'll get a non-smoking room, and if by chance some inconsiderate person smoked in your room before you.... they will do everything they can to move you to a better room.