Why would it be a bad idea? These blue sky presentations are made to very small, very niche groups. These aren't large scale announcements being made to the masses. These are basically insider sneak/peaks. When something makes it to ABC for a special presentation or makes it to features on the morning news shows, that's when they are making their mass announcements that they are offering to the world and those plans are locked in. D23 or other types of announcements to the fanatics are more general in nature, just talking about ideas, thoughts, plans. Emphasis on PLANS, these aren't guarantees. In the broad scheme of things D23 can be looked at as a free (hell people are actually paying to go) focus group for Disney. Some things may get green lit, some might not. It lets Disney get feedback and to build a buzz. And it gives people who are interested some thoughts on what is being considered. Nothing less, nothing more.