It ultimately won't happen (unless congress is unable to act due to bickering, which wouldn't entirely surprise me). The fact that they were released by the NMB from mediation into a cooling off period moved the ball quite a bit since the overwhelming majority of unions now have TAs...it is only about 2 of 12 unions who are still at a stalemate over sick time usage (sounds familiar). The other unions will honor any strikes though (think pilots honoring a mechanics strike), which will shut down the entire system.

I believe the last airline that entered a cooling off period was Spirit in 2010 and that resulted in a strike... so to say we would never be released (@Jim Rockford) is naive and cowardly.