I'm thinking 40-50 more chapters, but it's still hard to tell.
If u want my personal forecast: 30 chaps left for this phase of the succession war, but the next arc will also be on the black whale.
I imagine it like this: This arc will be concluded by Kurapika either reaching his goal to get the eyes from tserriednich or failing and being in dire trouble (maybe having to give up the eyes to save woble).
I dont think the succession war will be concluded in this arc tho. I think in the course of 30 chap, we are going to reach the refuel platform.
The arc will conclude and the next arc will focus on the zodiac and the mafia/hisoka/spider plot, with the zodiac having to contain a riot on the lower decks while the succession war still happens but takes a backseat, as in, it will be played out in a very different way than it is now.
It wont be a coincidence tserriednich, zhang lei and Luzurus are connected to mafia. I think with woble (and maybe fuugetsu) gone, only those will stay in the race by next arc's beginning who really want to be king and their mafia crews will play a role in the zodiac plot.
So the refuel platform and kurapika taking a backseat as MC in favor of zodiac/Leorio will mark the division between this arc and the next.