If a tablet is a reality for next year, then it would make perfect sense for them to announce it at WWDC. Then release it at a special event in March of 2010 after MacWorld. This would make perfect sense in the scheme of things considering how Apple has dropped out of MacWorld. They wouldn't want to be constrained by the scheduled date of MacWorld to deliver this product. If they can announce it at WWDC and then leave the delivery date open for "First half" of 2010, they are free to float that delivery date as necessary.