I think Kakashi is Kage material, but I don't think he'd ever become a Kage. I don't think we've seen Kakashi at his max yet. Kakashi is too lazy to go all out, and also too lazy to want to be a Kage. Kakashi has the potential, yes, but he won't be a Kage. Against other Kages, Kakashi would fair well, mainly because of his Sharingan abilities. Kakashi has brains and his talent with Sharingan, but he has low stamina and Chakra reserves. We'd never really know how he'd fair against the other Kages unless he fought them.