Hello Pipcard,
There's a fair amount of literature on this now, actually...you can get the
short version here by A.C.S. at The Economist, a
longer version here, a
broader piece at The Wilson Quarterly here.
It's a long-term problem, and one that makes big investments in risky, low-return ventures like manned space exploration less likely - entitlements for an aging population suck up a much big share of expenditures, and savings are being burned up rather than built up thanks to the same age cohort.
That said, I like the Fuji as well. But I think the authors are right that it's not likely to happen in this timeline, or any other where Japan's demographics are at all like ours.