Demurrage I believe is a maritime concept mainly used in the shipping industry when containers are held up in customs. I think #ergo some random crypto project uses this to avoid constant inflation.

I can see a future where the mother of all hard fork wars plays out where one side, (maybe BlackRock et al) push for unlocking satoshi's coins and demurrage seems like a plausible proposal for them.

Personally speaking I'm all up for a high tx fee environment and slow movement of bitcoin on the settlement layer while we transition to daily XMR usage. My bitcoin UTXOs are consolidated and I'm happy not transacting BTC as I place my long term bets in this regard.