Maybe he will form a pirate alliance with Law in order to counterbalance Luffy's excessive power. Otherwise I think both Kid and Law will be condemned to irrelevance on the World stage.
I don't think he'll do any more alliances as he already stated that he's sicked of it.
Become a Great Pirate and go ahead with his One Piece/Shanks objective
I think that just right after Wano, if someone will be considered a Great Pirate, it'll be Luffy alone. The others just don't have the achievements to be called like that yet, Luffy've got fame, territories and alliances, and most importantly Morgan
Also factoring in the fact that no one is able to solo a Yonko yet, it'll just reinforce my opinion on this aspect.
My expectation is that during his offscreen time, this is not anything other than my prediction, he'll become someone big in the underworld, as he already has connection with that world, and take over the weapon's trading routes of Kaido and the likes, because it's fitting imo. He might get his hands on Ceasar even, they'd hit it off, maybe... Anyway, I think he spends time nurturing his forces. And later comes back bigger than ever.
He might even take over Big Mom's big contacts in the Underworld, those guys at the Tea Party don't look like pushovers so ye, Big Boss Kidd, or maybe he'll enter in a partnership with Bege, not alliance but partnership as in they use each other openly so no backstabs.