I guess I mentioned the options were expired last weekend.
I thought you would get the answer by yourself by reading the article but you need to be told word by word:
To your question - How soon can we know if the option would be assigned or not (my broker is IB)?
Assuming that you are writing options: If the option is an American option, the buyers can exercise it anytime, which means you can get assigned any time until expiration. If the option is European the buyer will have to wait until expiration to exercise it, therefore you only can get assigned at expiration.
Having said that people normally exercise options when they are ITM, there's no point in exercising one that is OTM.
Particularly with IB there is a section under Account management called "Option Excercise" where you can see more details about your trade.
Don't like yourself that much if you are asking such a newbie question.