Sure, but we're talking about Monday, not the weekend. IF the weekend goes by with no trouble, they'll buy the market at the open on Monday. If something terrible happens over the weekend, obviously there won't be a big gap up Monday.
Steve, over on aj's thread, wrote yesterday that Monday's have been the strongest days for the market over the past 8 months. I think that has something to do with the fact that people are afraid to hold over the weekend because of terrorism fears, but that those factors are given less weight once the weekend passes without incident.
This is just a theory and I'm lacking in data to prove or disprove it at the moment.