Nothing. The guy who runs tzdata will be busy. Various things that hardcoded DST will break in six months. Hundreds of millions of people won't have a sleep disruption in the fall. Other countries may follow suit. Etc.
Daylight Savings has real effect on the northern states than southern states.
One of the arguments for Day light savings change is that -- it would still be dark during the time kids go to school in winter, early spring and late fall, many places in US will not have Sun rise at 8:00am. No matter how much we may be removed from the nature -- our wakeful hours are directly impacted by Sun rise and Sun set. On the other side, there are discomforts in moving the clock twice a year across the board.
The House undoubtedly will opt to keep standard time permanent.
The committee negotiating a unified bill will settle for a compromise of keeping standard time for 8 months of the year and daylight savings time for 4 months of the year on odd years and reversing the proportion during even years.
There will be intense discussion about whether to do anything special for leap years. After several months of back and forth, someone will point out that there are also leap seconds and leap microseconds, leading to further debate.
