[makx]

I can't speak for everyone, but among my foreigner friends almost nobody has a definitive plan to stay forever (though they may be open to the idea).

Permanent residency is mostly thought of as a relief from the stress of having to re-apply for visa extensions and not relying on having a job.

Until you get PR, you could be forced to leave Japan if you lose your job and don't find a new one right away.

[lance_klusener]

After PR is done, is there a set requirements to follow to become a Japanese citizen?

[laurieg]

PR is not a pre-requisite for citizenship. In fact, in some ways citizenship is easiest to apply for (you only need 5 years of residence vs PR's 10), though the application process is longer and more involved. Of course, you must give up all other citizenships so it is a decision not to be taken lightly.