Just my .02 but i don't think we will see any larger air-cooled motors from HD than the 110. They have too hard of a problem keeping them running cool as it is without increasing displacement.
Now maybe if they included dual oil coolers and the parade fan....
My prediction through my cloudy crystal ball with no help from those in the know at HD would be that they hold still until the introduction of a water cooled bike. They could make it larger displacement with lots more power to get the traditionalist to throw a leg over the new motor.
Younger riders would like the fact of the power and the ability to just buy the bike and turn the key and ride and not have to spend thousands just to get it to run right.
Larger air-cooled motors would give HD problems meeting EPA noise and pollution regulations. With water-cooled HD could sell lots of Screamin Eagle radiator fluid...