Maybe yes, maybe no. But if it’s challenged it’s still going to go before a judge who will be considering the most recent precedent in his/her decision making. And it doesn’t even need to be the DOJ making the challenge. Unions, state AGs, eleven PAX groups or other airlines who believe they may be adversely affected can get in the act.
Heck, after the Norteast Alliance ruling, AA may decide to challenge even this agreement. Even if they didn’t win they might delay it or force gate or slot concessions to get it approved. Or just drag it out a few years.