Actually in my experience the people who learn the language form a double distribution: those who are more educated/successful and those who have nothing but the will to survive. It happens in Spain, where poor foreigners know Spanish, highly educated ones also know Spanish, and the middle group can say some words or don't bother at all.

In Japan the main fear comes probably from China, since it's a lot easier for Chinese people to learn Japanese (similar characters) than for occidental people, and there is also a "relatively" high inmigration from poor Chinese people.

I have a sneaking suspicion that this whole "we will build robots to solve our demographic crisis" is just a ruse to allow entrenched corporate/political interests to continue down the softly-padded path to their graves, with the only cost being a few gimmicky displays of technology. This is not to mention that accomplishing their stated goal would require that Japan massively expand immigration to attract the necessary STEM talent. We in the west are probably being duped in the same fashion with all of the hype surrounding AI.