does most of this generation stay here or not?
oh, from what I know it all depends when they arrive in the US because once they are established (jobs, marriage, mortgage etc) most of them stay.
However, unlike the previous generation, the younger one is more prone to return to Poland since the system changed and there are more opportunities, especially for those who made some money in the US. But it is not an exodus as one would think.
I am sure there are some other people who would fill you in.
Just because they carry on with their culture in the US it doesn't mean that they will leave. I think they are- your friend is just being patriotic.