The only way I see replacement players providing any pressure to the PA is if the league generates decent enough revenue that makes the players consider that to the fans, they may be replaceable enough to move on from.
Furthermore, the NHL owners have a clear history. They got what they wanted with the last CBA, which the NHLPA has already said they would agree to play under on a temporary basis while negotiations on a new CBA are performed.
There is no way a court of law or the Review Board would side with the NHL Ownership Group on this issue. The NHLPA has already offered many concessions, the NHL has made virtually no concessions and is making no effort to make a deal happen.
This is basically my understanding as well. Securing an impasse ruling would seem a bit difficult for the NHL.