As far as I know, there hasn’t been any widely accepted plan or consensus to update the bitcoin protocol to replace lost bitcoins.
There shouldn't be one. If there was, it would also be possible to replace our own coins with others.
These coins, unless they are provably burnt using OP_RETURN, then they are just locked, until someone manages to unlock them, by brute-forcing private keys, or by solving the ECDLP. Both are highly unlikely, which means that these coins are probably "burnt" forever.