I can see what you are saying here, but the fact is the event has been listed most of the year and they stated they had big events planned for it, then cancelled 2 weeks before it happens.
In reference to the difference between GamesCom and Star Wars Celebration, sure SWC will have fewer attendees, but it is also a only 2.5 hour flight from Austin where as Germany is a good 12 to 13 hours. They likely have to pay fees to present at GamesCom, but with SWC, I suspect the fees would be nothing since it is put on by LucasArts. On top of that, SWTOR will be competing for gamers attention at GamesCom, but they would be the only one at SWC.
At the minimum, they should have a couple of people there, some vids of the game, etc. To help bring in more players.