With Oda seemingly regrouping everyone before the Onigashima battle(Kid, Jinbei and co coming one after the other), i think it's possible we might get to see Marco soon.
Nekomamushi is still nowhere to be seen, but unlikely that he'd miss the entry to Onigashima when he started his quest since Zou, with it being explained why it took him so long to come back
The problem though is last time we saw them, it was implied Marco wouldn't come. However considering Weevil is currently busy with the marines, maybe Oda could use this opportunity for Marco to be more involved?
I still doubt that Oda foreshadowed this since Zou, with ultimately Marco not coming. It's possible though that he'd only be reserved by the climax of the arc after settling things with Weevil