Unlikely. Population is declining precipitously. The rate of reproduction has plummeted in Japan. There aren't nearly as many young people as there used to be. Why would they want to stay in a declining country rather than go to places where conformity is not prized, being an entrepreneur is prized, and there is a growing market?
Irrelevant. There's no link between population decline and startup culture. There are still millions of young people growing up over there. There are multiple reasons not to go to the US, with language and atrocious visas at the top of the list.
Err, is too. As one simple example, when the electorate is heavily skewed towards older people (and in Japan, and this skew is further exacerbated by how low-density rural areas have higher weight in the Diet), politicians will enact policies that favor the elderly at the expense of the young, Japan's increasingly Ponzi-like public pension scheme being a prime example.
The pension scheme is a bad example as it was put in place in 1961[1] long before Japan experienced it current population decline. Furthermore recent government actions have been towards weakening the yen which will adversely effect the elderly and pensioners (who are on fixed incomes).
Unlike the US, there does seem to be a recognition that people are part of the economy of the country and that there are mutual shared interests in making things work. The issue seems to be more in the speed and adeptness at which changes are made.
That being said, the biggest obstacle to start-ups in Japan is the Japanese aversion to risk. The most talented people would rather work for peanuts in large Corporations or in secure Government jobs rather then risk failure in a start-up.
Policies that encourage internships and entry level recruitment of young workers. Policies that encourage the supply of child care, schools, university access and other services to support families. Access to family medical insurance.
I met expats, immigrants, students from all over the world in Europe, but I didn't ever met one from Japan. Anecdotal, I know, but maybe Japan is so special that emigrating from there feels like leaving Earth.
Nitpick: emigrating means moving away for good, and relatively few people from developed countries emigrate in that sense. Perhaps you mean living abroad for study or work, being an expat or something similar.
I think there are 2 big reasons why you won't find many Japanese expats in Europe. One is the real or perceived language barrier. The level of English education in Japan is pretty low, and even people who speak passable English tend to be not confident about it.
The other reason is outlined in the article. Going abroad for college isn't prized as it is in (say) China. You're deviating from the path that society expects you to follow. You might even get strange ideas about life/work balance. Going abroad for a "skip year" sounds even worse.
