Demand is likely to increase overall during the day, which will be good news for Genesis, as the national demand will be flatter overall. The actual peak demand in the evening probably wont be affected too much.
It will be very much a wait and see game as a lot of small commercial businesses possibly wont re-open yet. Those that do open tend to close around 5:00 pm or shortly after, and the decrease in demand there helps to offset the rapid increase in domestic demand between 5:00 and 6:00 pm.
It will be difficult for both Genesis and Contact to get their gas demand right for the first couple of days and I can see some frantic gas trading occurring, but the difference in revenue for a few days will be small compared to rest of the year.