Specify removal

specs/fjord/exec-engine.md

@@ -76,4 +76,5 @@ multiplying the `estimatedSize` of the transaction from the above L1 cost formul
 of the bytes in the compressed data are non-zero.
 
 The `L1GasUsed` property will be deprecated due to it not accurately calculating the L1 gas used
-by a transaction. Users can continue to use the `L1Fee` field to retrieve the L1 fee for a given transaction.
+by a transaction. Users can continue to use the `L1Fee` field to retrieve the L1 fee for a given transaction. This field
+will be removed in a future network upgrade.

specs/fjord/predeploys.md

@@ -72,6 +72,6 @@ function getL1GasUsed(bytes memory _data) public view returns (uint256) {
 ```
 
 The `getL1GasUsed` method will be deprecated. This is due to it not accurately estimating the
-L1 gas used, for a transaction.
+L1 gas used, for a transaction. In a future network upgrade this function will revert when called.
 
 Users can continue to use the `getL1FeeUpperBound` or `getL1Fee` method to estimate the L1 fee for a given transaction.