Interesting question:

I think there will be two dynamics that will play a role:

1) Lightning Network yield on liquidity as the new risk free rate: Once it will be possible to generate a stable and reliable return on Lightning liquidity this will establish itself as the new risk free rate return on money. This yield will fluctuate as the confidence in the economy fluctuates, similar to how bond yields fluctuate today. So the more interesting question may be, what percent of BTC on the lightning network will serve as liquidity supporting transactions vs cash for spending. I suspect that a lot of it will be locked in at any given point and people will only withdraw what they need for spending on a monthly basis.

2) Safety of custodial Lightning BTC vs cold storage BTC: If custodial Lightning BTC reaches a point where people feel it’s similarly safe as cold storage on chain BTC (I don’t know the likelihood of that), the ratio that remains in cold storage could get very very low because it doesn’t return any yield. In that scenario I suppose the only BTC remaining in cold storage at any given point would be what’s needed to open and close new lightning channels.

CC #[2]