Well, the E3 absence had a big part in setting up high expectations for Gamescom. Personally, I didn't expect much of anything (my feeling is that their cards had already been shown with the public demo and ensuing update....it's now time to tune things and focus on finishing the game), but then again, I have no emotional investment in FFXV aside from wanting it to succeed and bring back some enthusiasm for Japanese development.
At the end of the day, I think there's still a problem with PR/marketing trying to heat things up and development struggling to move fast enough to catch up (in which case, they'd be inclined not to disturb development too much when preparing for public events). I guess we can pick our poison: radio silence for lengthy periods or lots of PR with erratic timing in terms of new things to show. Either way, fans can get pretty pissed, even taking it personally as some kind of maliciousness.