Demographics pose a serious threat to the long-term health of the otaku market in Japan. The birth rate
continues to decline, and Japan's population becomes older and older. Since anime viewing
falls with age, the market for anime in Japan will inevitably shrink in the years ahead. Of course, this is a slow, extended process, not something that will force studios to close their doors in the next twelve months.
One compensating factor that's often discussed is the tendency for younger Japanese adults to
remain at home with their parents. Nearly three out of five 25-29 year-old men are still living at home along with just under half of the women.* Young people living at home presumably have more money to spend on entertainment than they would if they were building a family and establishing a household.
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*Comparable data for the US were harder to find, probably because the incidence of adult children living at home is so much lower. From Table F1 in this report by the Census Bureau, roughly five million households had a child over 25 years of age at home, or some 6% of the estimated 78 million "family" households in 2008, with another 8% having a child between 18 and 25.