Might not fear of a change failing to deliver anything better and costing the club be holding back the board?
The board may not stand in McCall's way out the door, but is there any point in appointing someone else after the transfer window closes? You can (if you're a "see you next tuesday") always bring in a successor as a coach while the current boss is here.
IF (a big if) home league form can secure 7th or 8th this season, then this will be accepted as a success IMHO. Performances don't matter, just points.