I believe the answer to your question would be when the big supermarkets accept some form of btc for their goods.
This is a good point because we all know that not all people knows anything about bitcoins and there are people that doesn't hear anything about bitcoins and they didn't know that there are kind of money that are existing just like that. But if there are bit establishments that will accepts bitcoina as a payment and they have that advertising in the stores then of course the people will get curious and then they will start asking about it and they will start using it so that will be really helpfull for that thing to happen.