If they do go to 5-day delivery, you can bet it won't be Monday - Friday. That would make a lot of sense, as it would be less disruption for business mail. Also, the employees would love it. And therein lies the reason for not doing it. Postal management goes out of its way to screw over the employees any time it's possible, and this would be one of those times. I worked there for 31+ years, hanging on strictly for the pension I now enjoy. It ain't easy to work and try to do a job when the bosses don't care about anything but their pay, and sabotage your every move, basically making working there a thoroughly bad experience. This management style is the reason the postal circus is what it is.
Who gets bonuses?? Upper management gets bonuses. Millions, for the excellent jobs they do as managers presumably. They sit in their offices shuffling paper and trying to figure out new and better ways to screw the people doing the work, and get bonuses for it.
Working there sucks! Reminds me very much of that guy "Onie" that Johnny Cash sang about. The workers get the mail delivered IN SPITE OF the "managers".