However, there are a couple of things that could save the PS4.
Getting a bit ahead of yourself, don't you think? The console isn't even out in Japan yet, but, assuming its US/European success continues, it should be attractive to Japanese publishers interested in selling the rights to their games to US publishers.
This was one of the biggest reasons the DS and 3DS did so well in regards to Japanese developers, while the PS3 didn't. Many Japanese developers don't have the resources to develop for more than one platform, so if they're interested in selling international publishing rights they have to stick to platforms that are also a success in the United States.
The PS3 was 2nd or 3rd place in the United States, even if it eeked out the number one spot world wide. As such, it wasn't an attractive place to develop games, unless, a developer had no interest in selling their publishing rights. The PS4 however, it likely to be fairly successful in the US and Europe, so as long as it has a healthy install base in Japan, it'll make sense to develop games for the platform.
I might also add, Lightning Returns wasn't expected to sell well, I have no idea why Square thought making yet another direct 13 sequel was a good idea. FFXIV however, was one of the more successful games released in Japan this summer, and sold extremely well in the country, for an MMO.
So I think the situation, serves more as a refutation of direct Final Fantasy sequels, rather than a refutation of the brand altogether.
I do agree however, that Japan has severe structural problems, that they need to address.