On bitcointalk, the best options to earn btc is the Signature campaigns. What you need to do is that if you are a good poster, just buy a full or senior member account and join in a best campaign which will pay you more for max posts.
You are right that the best option here in forum is to join some good signature campaigns but don't always rely on it as you don't know until when they are going to operate. It is better if you are going to have a good source of income here in forum. Just like doing some editing skills or creating a thread for a company.
I don't think that we should worry about the future of signature campaign as they will operate for a long time and if one campaign disappears there will always other which will take care of us.