Before you take them serious and then alter your positions because of that, then you need to ask yourself the question, who will bear the brunt of whatever will happen then you go ahead. Its no doubt that these people have a lot of followers and express optimism in what they believe in. Just a like politicians will stand in rallies to claim the amount of landslide victory their parties would make in the forth coming election, they forget that the winning party is actually decided by the population who will cast their votes. They have only expressed their opinions, and the possibility of that happening is not a function of opinions but factors that are even beyond what they can control. If factors work in their favor, and their prediction came to pass, then they are seers if otherwise, its just mere predictions not supported by reality.