The number of states with comprehensive indoor smoking bans went from zero in 2000 to 25 in 2010.
"It is by no means a foregone conclusion that we'll get there by 2020," said Dr. Tim McAfee, the director of the Centers for Disease Control and Prevention Office on Smoking and Health.
But the success of the smoking ban movement has been astounding, and seems to be accelerating, he added. "I'm relatively bullish we'll at least get close to that number."
Nearly half of U.S. residents are covered by comprehensive state or local indoor smoking bans, the CDC estimated, in a new report.
Another 10 states have laws that ban smoking in workplaces, bars or restaurants, but not in all three venues.
Some other states have less restrictive laws, such as requiring smoking areas with separate ventilation.
Only seven states have no indoor smoking restrictions, although some of their cities do: Indiana, Kentucky, Mississippi, South Carolina, Texas, West Virginia and Wyoming.
Gary Nolan, the director of a smokers' rights group, said he wouldn't be surprised if the CDC's prediction came true. Public health officials and others have been putting tremendous pressure on bars and businesses to bar smoking, he added.
"It wouldn't surprise me if they prevailed," said Nolan, of the Smoker's Club. "It's just a little bit more liberty slipping away at the hands of big government."
Tobacco smoke is an established cause of lung cancer, heart disease and other maladies, and smoking has been called one of the nation's leading causes of death.