As we know Sasuke Uchiha was still a Genin when he left the village. By the end of Naruto Uzumaki, Naruto was still a Genin, never got a promotion. Sasuke Uchiha left to travel the world not long after the war so going by the fact that Naruto Uzumaki had been back for a year (I think?) and still had not received a promotion I like to believe Sasuke Uchiha’s chances of getting a promotion for the short time he’d come back and with all the F’d up stuff he did are slim to none, and I highly doubt he came back to participate in any Chunin exams either. With all that said I like to believe that Kakashi Hatake never got around to giving him a promotion either, so by the time Uzumaki Naruto became Hokage, Sasuke Uchiha is still a genin (unless something official says otherwise?).
Uzumaki Naruto now Hokage, so Naruto Uzumaki Definitely not a Genin anymore that would make Sasuke Uchiha the last of the Rookie-9 a Genin, and knowing Uzumaki Naruto he’d totally prank about Sasuke Uchiha by not giving him a promotion (Jonin) either.
This is all just speculation about something that I think is quite funny if true and wanted to share it with other fans. None of this is fact just speculation from a mad fans head.