This.
He does have a sense of leadership in him which is great for the team IMO, but he will most likely never be the captain of Barcelona.
Why not? He's going from the ground up right now but with a good trajectory he's in the right range age/experience wise to be leading the next generation in the future at a certain point in time. He has the character for it.
In his first season all it'll take is a great attitude and consistent performances and/or gradual improvement (plus the occasional wonder-game where he bails us out) to make an impression on his teammates and the coach. After that he's settled in and gradually acts more vocal becoming one of our 'insiders', giving him an actual role in the dressing room. He does that for 2-3 years increasing his importance more and more along the way and then he'll be about 25/26 years old which is still pretty early in his career.
By then it's 4 years down the line total and he's theoretically an integral member of the team and the dressing room. Having experienced triumphant successes and tragic failures with his teammates he's built a fairly strong bond with them. Marc, being a pretty sentimental guy (shown by his dedication to Mönchengladbach) is self-sacrificial in attitude and has a dominant enough character to influence others. This is at a time where our bigger veterans (Iniesta, Masch, etc.) are close to retirement and playing less or have already left while other seasoned stars (Busi, Pique, Messi) don't have the profile of a captain. His tenure at the club is in the right transition period to be at his peak when the older generation is dying out and the younger generation doesn't have seniority to him.
At that point he's clocked in enough years to not be viewed as an outsider, rather an important inside member of the team. Sure he won't ever have the 'La Masia' label but there are many other more significant attributes to have for captaincy. The coach, whoever it is at that point (though I hope Lucho can be enough of a success to stay for a long time, tired of the managerial merry-go-round) won't have that bias towards the older golden generation that we do right now so MAtS should get a fair shot even if he isn't the oldest player in the squad. There might be some other obstacles (appreciation for Messi's abilities may one day faultily portray him as "captain material" just because he's our star) but it's certainly not out of the question that it'll happen.