Zero until the earth exists and there is life in it and there is internet service available. Bitcoin might only go extinct if the whole world, every single person and entity, starts using Bitcoin all of a sudden, the markets stop because people stop buying and selling, and the blockchain stops because no transactions are being done. That is when Bitcoin might die, and what are the odds for that happening? In my point of view, none.This thing might happen in the distant future where there might be a better technology and something much better than Bitcoin is invented and people leave Bitcoin and start using that and Bitcoin dies off like a meme coin which doesn't get enough attention and eventually dies.