I think that the days of air cooled bikes (particularly over about 200cc) are going to be numbered - With the even more stringent EU-4 level of noise and emissions requirements for motor vehicles, it may become impossible for anything larger to meet the specs. It was the primary reason for H-D to redesign their "Milwaukee-8" engine, and I think that even then, the non-liquid cooled one may be hanging by a thread as far as comfortably passing the tests goes.
In another ~15 years, we'll probably all be forced to buy electric motorcycles. This might not be a totally bad thing, depending on their range, etc.
