When Will The Markets Be Open 24/7?
The stock market trading day is largely an artifact of how stock exchanges functioned when all the trades were done in person by market makers and specialists. But as the major bourses have gone more and more to automating the matching of buyers and sellers, there is no great reason for this to continue. Likewise, the three day settling period for trades dates back to when the stock certificates were manually transported between brokerage houses and the "cage" where the clerks labored.
There isn't really a reason for either any more and I expect that the bourses will be open pretty much all the time with trades settling that day. (Maybe a scheduled down time Sunday night for database maintenance and software installs and the like.)
It will probably be a non-US bourse that is the first to take the plunge, but all the bourses will have to follow suit.