If we switch to a high-pressing style (as Ole seems to like talking about), I can't see how Martial will have a place at the club in the medium to long term.
Martial is an old fashioned luxury forward in a footballing world where luxuries don't exist anymore.
All the top top 4 play a high-pressing style, and between them they've taken every major trophy available to English clubs at home and in Europe. I'm pretty sure that's the template that the United coaching staff are hoping to emulate.
But on the specific point of Martial, #9 during the early 2000s would have been his most natural position. In the latter half of that decade, a lot more teams started playing target men who brought goal scoring wingers into box. In that situation, wide forward (#7 or #11) would have been Martial's best position (which is what LvG did with him, being the managerial dinosaur that he was). Martial is a player that likes to wait for the ball to come to him, and doesn't like to worry about the ball when it's not already at his feet. Systems to accomodate him don't exist anymore at the top end of the game.
In 2019? I'm not sure he has a seat at the elite table. If he'd been born 20 years earlier, he'd have been sat next to the best.