I just started reading "A.D. - after disclosure" by Richard Dolan. It is an attempt to rationally predict what will ( or would, depending on your viewpoint) happen when authorities around the world admit that extraterrestrials exist and first contact happens.
Will markets crash? Will religions collapse? Will people get up and got to work? It uses recent studies and opinion polls to establish reasonable answers. The most surprizing to me is their conclusion that religions will not be affected, at least right away.
It does, however, reason that this "event" will likely be the turning point of human history - we are not alone. This is why it's referred to as "A.D." in part because it would be pivotal , as with the coming of Christ in history.
They offer no solid predictions as to time but do offer many reasonable scenarios on how the matter might play out.
metatron