Newark is going to open in a few weeks’ time and Houston will open over the summer. The Los Angeles Polaris lounge is supposed to open later this year. So if they stick to that schedule United should have 5 Polaris lounges open by the end of 2018.
However we’re not going to see any more in 2019. The next batch won’t open until 2020, which considering these were announced nearly two years ago seems insane.