Is it too early for me to book a flight (for this June) to Europe? If I wait, will the prices go down or up?

I've heard conflicting reports -- some industry people say if you wait another month or two before booking your flight, the airfare prices may drop, b/c right now it's kind of early for the airlines to predict how business is going to be... And other industry people say that summer prices are all fundamentally the same, and the longer you wait, the more you'll be paying. What do you guys think?