First of all, I don't believe 5 day delivery will pass. Congress can't agree on which day they will phase out (some believe the PO shouldn't close 2 days in a row every week and want Tue, Wed or Thu to be the day phased out), there have been no details as to whether or not we would work 4 days or 5 if it ever passed, Susan Collins has told Potter that it won't make it out of committee, and even if it does, it doesn't have 60 votes to kill a Senate fillibuster.
The PO hasn't given us any details, but you can bet it will be a disaster for us. It's in our contract that they can renegotiate the time standards if we ever do go to 5 day delivery, and that won't be pretty. To answer your question, I'd say the NRLCA has been working hard on Capitol Hill to make sure it doesn't pass in the first place, which would be good news for subs and regulars alike.