This seems like a problem with the UX of KickStarter and not project creators. Instead of asking a creator to predict the future with relative accuracy, instead model development like real life. If project creators were prompted with two questions asking when your product would be shipped if everything goes (right||wrong) then you would have a more realistic shipment range, and more products would ship "on-time". Backers would have more realistic expectations for product shipments, and wouldn't panic when the first deadline is missed.