Well, the EWR-HKG route is currently covered with the 77W, the 777-300ER. These planes are only available with the Polaris / PE layout because they are relatively new to the fleet.
The sCO 772 resumes on this route on the westbound departure from EWR on 27-Oct-19, which is one day after the SFO/HKG route looses its 77W and goes to a Polaris 772 twice daily. While I'm sure the changes are related, I can't explain how SFO going from a 77W to 2X 772s causes EWR to loose its 77W. I would assume this is just the date for the fall schedules to go into effect.
Related to your question, since SFO/HKG is going to utilize 4 Polaris 772s (2 per day, both directions), and there are only 5 of them in service now, I would expect the sCO 772 and be delighted if a Polaris bird appears on your flight. Keep in mind that there will probably be a few more retrofitted by then, but the ones not dedicated to flights with PE service will be few and far between.
If you're really interested in flying in Polaris, the only way to guarantee that now is to do a connection in SFO.