Well he has said he will be announcing his decision on Tuesday at least, there is little point in reading rumors etc till then as we find out then and only then 100%.
Regards reasons for him possibly not taking it I can see it being due to Van Gaal if he is taking over as director of football.
He likes to be top dog and has fell out with people everywhere he has been. He is strong headed and very old school. The players certainly would not know what hit them if he was in charge. I think he would want Martinez out of the way and want to be manager himself. I do not think in that role of director of football he would get along with the likes of Martinez and Rafa with these guys also wanting transfers control etc.