I am in agreement with Dave. Airfare costs are a big deterrent for people flying to Asia. Even more of a deterrent is the duration of the flights. As I get older I am having more problems with a twelve to sixteen hour flight. Ten years ago it didn't bother me, but on my last trip to Singapore the flight from Tokyo to Singapore seemed endless.
There are many American's that do not like to fly nor do they feel they want to go somewhere that requires a passport. Flying and having a passport have been part of my life since I was eighteen years old so I have no problem with it.
The people who will have the biggest problem with the "new" ships going to somewhere other than America are the long time cruisers who have been used to getting the first shot at the newbuilds.
There are also a lot of half-truths about Asia. Yes: There are some parts that are dirty and not too fun to go to but there are MANY cities, countries and areas that would put American cities to shame. Singapore, Hong Kong, Shanghai are just a few. Singapore is not my favorite city in Asia and one of the reasons is that it seems too "sterile". The Hawker Stalls or Food Centers were my favorite thing in Singapore because they gave you a true feel of Asian food and culture. Most of the other sites and restaurants in Singapore reminded me of high end restaurants in Chicago or New York.
I still love Hong Kong because you can find the real neighborhoods. Here you can shop with the locals, eat in their restaurants and have a great time.
Of any area I love Asia more than Europe. There are still many parts of Asia that are not "Westernized". Europe is becoming more America with old architecture and less foreign.