Is this term actually used widely through Japanese culture or are they just riding the popularity train? E.g. if I'm in a "planning your future career" class in a high school in Japan, is the concept of ikigai going to come up?
It's a normal word/concept that everyone's familiar with.
As for career planning, I don't think it's very relevant. The sorta-equivalent sayings like "do what you love and you'll never work a day in your life!" tend to be used in a way that puts existing preferences and interests first, and everything else as a consequence of it. The way I'd think of "ikigai" in a career context, the work being meaningful (as in the opposite of a "bullshit job") is what comes first. Since it's meaningful, it's something the world needs, so you can get paid for it. Since it's the opposite of a bullshit job, you're motivated to devote the time and effort and attention to be(come) good at it. A job well-done is satisfying. So I'd envision it as something you settle into, rather than plan ahead with your guidance counselor equivalent.
It's also not necessarily a word specific to jobs/careers in the first place, and in a literal sense only means "I live for this" / "it's worth living for". The rest is a recent fixation by writers.
Most Japanese people do not use this term, and I'm fairly certain most Japanese people don't even really know the word. This is one of those "Big in Japan" things, except, uh, "Big outside Japan".
Source: live in Japan, have asked Japanese people around me if they know about this concept (that is popular in USA). Usually hear: へ〜、全然知らない。
The topic came up again and maybe this has been changing lately. I downgrade my above comment. I still think that it got popular in the U.S. first and then propagated back to Japan but ¯\_(ツ)_/¯.
Back in reality, the word is more commonly used in the expression 生き甲斐がある (ikigai ga aru) which means roughly "Life is good", "I'm glad to be alive", which you might use after sipping a really good beer for example.
