Yes, everyone knows that, yet no one knows how long they are going to do that. They might stop to 50% like some projects or keep going indefinitely. What i would like to know why they are not answering to this. They are not committed to any number so they might just stop burning after 40% for all we know. They have never promised to keep going indefinitely, and at some point there are no team tokens to be burned.
I think if they decide to stop burning BFG tokens, they will first ask the community about it and create a vote.
As it was when they decided to extend the mining period for BFG tokens.