No idea. Oda is rushing, so there is no way to say.
He at least should deal with the things he already set up for a long time, but if he ever will, who knows.
For example, from the answers here, people are sleeping on Kuma and Vegapunk, who should get their own arc, even if it is only a PH length arc.
Vegapunk has been around as name for 600 chapters, Kuma even earlier and way planned from the beginning. I see a SSG Revo Vegapunk Kuma (lvl 6 prisoners) arc.
And if SSG really can replace or even overshadow the Shichibukai, they are strong enough as opponents.
Elbaf has to be seen one way or the other.
And final war and everything connected to it, which is a long list in itself.
Other than these, i dont think there is anything that has been built up before. Stuff like Emerald City can stay as concept/myth without any problems.