It's more likely that "lost bitcoin" will be forked so they are lost forever, or never spendable than being folded back into mining rewards.

Instead of mining, people can be brute-forcing the private keys to all those P2PK bitcoins and that may happen in the future but it will happen naturally with no fork.

This has been discussed plenty of times, and while some may agree that lost bitcoin remain lost, almost no one will want 10 or 20 year untouched coins to be "found" by forking a new altcoin. It may happen, but it's not going to be bitcoin. (There was some alt called Bitcoin Unlimited by Jeff Garzik.)