The aggregate demand for ETH from fees on L2s could potentially offset the reduced fee activity on Ethereum's mainnet, as most L2s utilize ETH for fees and collateral.
"almost every single layer two on ethereum leverages eth for fees and also as collateral in its D5 protocols with enough adoption it's possible that the aggregate demand for eth arising from fees on its layer 2os will be enough to offset the absence of fee activity on the layer one"
