I think in the future companies will realize they can retain exceptional talent by implementing a four day work week. As more and more hackers get older and have kids they will be drawn to companies that support an actual work/life balance, as opposed to the status quo of "its startup life of course you work 60 hour weeks."
That's assuming that you are not expected to simply extend the hours in those 4 days so that your hours per week remain the same or decrease only slightly. . .as some companies currently do.
