It's conceptually possible he could end up in some sort of important appointed position. Significantly less so than if he had dropped and endorsed earlier than he did,* but possible. Better odds to have some degree of influence in such matters. Kinda' unlikely either way, though. Not only is he almost certainly more useful to the party in the senate by a significant degree, he's not exactly been doing the most bang up job of building bridges with other politicians. Political capital the guy could expend to nudge some people around position wise is... probably not sufficient to do much. And beyond that, again, the guy's desired policies are not very different from the democrat ones -- just about anyone clinton will put in a position is someone sanders probably doesn't have much of a problem with, or would have recommended anyway.
S'just... you could probably comfortably say sanders came out of this primary better off than he was, so far as political influence goes, but it's also pretty damn certain he's came out a lot worse than he could have. Made some pretty notable mistakes, ones that are painfully obvious even to political plebs like, well. Me. And beyond that the guy is only nominally a democrat at this point. His party influence and general political influence over fellow politicians is... probably not going to be that great. If he decides to go independent again any time soon it'll frankly become kinda' shit, t'boot.
*His bargaining position became increasingly weak as his loss became increasingly certain, and he held on a lot longer than he probably should have, so far as that aspect of things goes.