Aproximately 30-50% are out of circulation already. If a bitcoin is lost, than it's lost forever. It's out, no way to get it back.

Here's good infographic explaining everything:
https://imagesvc.timeincapp.com/v3/mm/image?url=https%3A%2F%2Ffortunedotcom.files.wordpress.com%2F2017%2F11%2Flost_bitcoins.png&w=800&q=85