Update EIP-7069: clarify EOF vs 7069 interactions

Merged by EIP-Bot.

EIPS/eip-7069.md

@@ -55,6 +55,8 @@ We introduce four new instructions:
 - `EXTSTATICCALL` (`0xfb`) with arguments `(target_address, input_offset, input_size)`
 - `RETURNDATALOAD` (`0xf7`) with argument `offset`
 
+In case this EIP is included as part of the greater EOF upgrade, these four new instructions are undefined in legacy code and only available in EOF code.
+
 Execution semantics of `EXT*CALL`:
 
 1. Charge `WARM_STORAGE_READ_COST` (100) gas.
@@ -180,6 +182,10 @@ When existing `CALL` series operations encounter an address that does not fit in
 
 Smart contract developers should not rely on the operation reverting when such addresses are passed in. When a suitable proposal for the use of Address Space Extension is adopted it is expected that the `EXT*CALL` series of operations will adopt those changes.
 
+### New instructions undefined in legacy (only if this EIP is part of EOF)
+
+There is an alternative scenario where, in case this EIP is included as part of the greater EOF upgrade, the four new instructions are **additionally** available in legacy EVM. There is, however, a preference to limit changes to legacy EVM in the fork where EOF is included as well as in subsequent ones.
+
 ## Backwards Compatibility
 
 No existing instructions are changed and so we do not think any backwards compatibility issues can occur.