Honestly, I don't really care whether the Emperor Demise event will return or not. I spent 200 crystals daily on farming Lando and will get the emperor to 6* before the event ends.
As a temporary event, I will get three 6* iconic characters including ST Han, Lando and the emperor. It is certainly worth more than the total 2,000 crystals I will spend. The fact is that temporary event is never worth spending money due to its relatively high cost!
However, if it ever comes back. It won't cost me anything to get the emperor to 7*. So, let's gamble with the dev.
More important, I don't want to become one of the players that encourage the dev to schedule more short notice temporary events by spending on this event.
Keeping us in the dark is the only advantage they have against us. We don't know what and when will be the next event!