Experts can become very, very good at reading the immediate situation and handling it well. But their intuition for handling long-range problems seldom has the opportunity to develop. However, their confidence is high. Daniel Kahneman says "They know they are skilled but they don't necessarily know the boundaries of their skill."
The halo effect (transferring unearned value), combined with our WYSIATI tendency (assuming 'what you see is all there is'), often leads us to make very bad marketing forecasts. Expecting to fail, and planning to learn from your failure, is a much better strategy.
Kahneman recommends that we develop a checklist of reliable and non-overlapping traits that we expect to see in a venture, and apply that checklist ruthlessly before we decide whether on not we expect it to succeed. If we become experienced using the checklist we can give the traits a weight, but we need to make sure they vary independently. Using this method, your decision to launch a product would not be based on expectation of success, but based on whether or not the project represented a meaningful experiment--something you could learn from.