If the PA accepts the terms, they protect the players already under contract and life goes on. Players will still be able to sign these mega deals, albeit with a higher cap hit.
If they fight, they throw Luongo, Kovalchuk, and Hossa under the bus. Luongo would probably lose millions, and Kovalchuk would probably lose millions and be forced to the KHL (by his own crazy demands). They already lost in arbitration, so they can't bank on that to salvage the deals under threat and any arbitrator with common sense will see them as circumvention. More arbitration losses would greatly reduce the chances of any player signing one of these front-loaded mega deals in the next couple years, which is ostensibly what they would be fighting for by rejecting the ultimatum.
I think they'll elect to protect the players that already have contracts, but nothing will shock me at this point.