That post doesn't address the underlying problem. How is the new signature opcodes introduced? How is consensus reached among a mix of nodes that may or may not

That post doesn't address the underlying problem. How is the new signature opcodes introduced? How is consensus reached among a mix of nodes that may or may not understand the new signature scheme? Back in 2010 this could have been handled by hard-forking and requiring everyone to upgrade. In fact in the very early days there were various hard-fork changes that were not even well documented at the time - you simply upgraded your client and things worked. That is no longer an option: the bitcoin ecosystem is simply too big. Since then we've worked out ways in which soft-fork changes can be introduced which do not result in consensus errors. This was first tested in the wild with pay-to-script-hash in 2012. P2SH outputs are treated as anyone-can-claim outputs by older clients. More recently there has been work on proposals for adding Lamport signatures without the introduction of new opcodes. This is all definitely new work.