Why does he need an extension? If he starts the season poorly then we'll be in the same "too expensive to sack" problem that potentially kept him in the job during the abysmal 23 game sequence that only ended a couple of months ago. He has a contract that covers the next 12 months, doing nothing is a perfectly valid option for a club with our budget and recent record.
He and his agent have been banging the "clarification" drum so loud that many seem to have forgotten that he can simply get his head down and do the job he's paid for (as many demand our players do whenever disputes arise), that's the default option for all concerned.
Players sign for clubs knowing that any manager could be gone before they know it. Only 26/72 managers in the EFL have been in the job longer than 12 months. Only 14 have survived 2 years (Martin is 15th longest-serving). How much "clarification" does an extended contract actually provide these days?