Multiplayer is most certainly a big announcement... but why postpone it till "later in August"? There are a lot of people who are practically begging for MP and wouldn't it make sense to announce it during GamesCom? Fans would have been sooo happy.
Personally, I don't need MP to feel happy so I would not be bothered if MP is not announced. There are other things I'd like to hear: more info on crafting system or character creation, early Keep open beta. Though, only the last one counts as "big announcement".
Anyway, we have three months till the launch date and plenty of time for other announcements. If it's MP, then fine; if it is not - great! It can be something completely unexpected. I don't know, toolkit (they said the game is unmoddable, but who knows, right?) or this companion app (still don't understand what is it - the description in the interview was rather vague).