I suppose the similarity between KH2 and KH3 you could argue is how unpredictably information has been released for both games during their marketing. I remember waiting and waiting for KH2 news and at the time no one knew if it would turn up at the big events and more importantly what they would show! The other thing I remember as well about KH2's release is that the Japan release date was announced at TGS 2005 in September...... for December....that is a gap of 2-3 months! For that to happen now would be crazy of course but back then I remember it felt wow thinking we would finally see the game release in just a few months. That won't happen now but both games have had streaks of unpredictability with the way Square and Nomura have released information and when.
Also just a note, the Kingdom Hearts event for the Japan D23 is the only KH related thing at that time we will be getting information. I don't believe there is anything else during D23 Japan where that will happen since it will be mostly Disney and Disneyland-focused stuffs.