It would at this point not surprise me if Hisoka was not even on the ship anymore but actually left some time ago and is waiting at the Black Whale's destination.
I do think it is a character we've seen before though. Or at least that his location has been foreshadowed. This is assuming the arc is not going to be as long as it very well could. Togashi could easily extend it by a LOT, given how the Succession War played out. (I really loved the SW back in the day, but as the years drag I guess I find it less appealing, assuming it doesn't get more hectic or complex.
What I'm assuming is, Hisoka used his official Hunter status to get to the highest level of the ship, which is clearly meant to detach from the Black Whale (which is probably a play on words for Togashi, because without the eyes and mouth, the Whale would clearly be a black pearl. you know, those cursed objects?
Ever since its reveal, the Black Whale just had "death trap" written all over it. And so far that has been the promise from Hyui Go Ro. The entire ship is a sacrifice. But I think that the ocean liner on top of the Black Whale is separate enough that it simply will remain afloat while everything else just... sinks.
In this scenario, Hisoka, being the master analyst that he is, will just wait aboard the only safe part of the boat. It is also where the princes are. He knows the Spiders would go for treasure if able. So he's already waiting where he knows they will show up eventually anyway, to maybe get the drop on them.
There will almost assuredly be a link-up between Tserriednick and Chrollo. The fortunes given by the mafia lord's daughter are still accurate. Actually, they more accurately depict what is happening on Black Whale than before. Basically, it is the idea that you can indeed change the future, but you can never halt Destiny. Basically, if the predictions are absolute, it means it is tapping into the concept of Fate or Destiny. It is possible, I think, to change such forces in one's life, but unlike general future events in a given situation (like Yorkshin), Destiny requires a more absolute effort, because it is an overarching force or scenario. It would be like insisting you can go the rest of your life without ever getting wet, but then insist on living somewhere known for its rainy season.
Basically, the Spiders could indeed avoid the "fate" revealed to them by the fortunes. But ONLY if they heed the warnings and make the necessary changes. If they disbanded the Spider, took lives up elsewhere and Chrollo did something to ensure he NEVER could go "east" again, literally or figuratively, then maybe he could avoid whatever awaits him and the Spiders.
Some have more to fear than others, like the vacuum girl (I used to know all their names, too, goodness, how life erodes memories). She basically is "destined" to die alone in a room filled with merchandise. Which means reality itself is worked toward that end. It can be struggled against, sure, but it is no different than being bodily assaulted or raped. There is only so much you can avoid if you're not willing to totally prevent the destined scenario, even harder if you're not aware of it...
At any rate, my point with that talk about the fortunes is that maybe Tserriednick plays a major role with the Spiders, because I recall there being something in Chrollo's prophesy. And I'd feel like Tserried is being set up either as the main villain of this arc, or a major one in the future. His powers are just too scary and reality dominating. For the Succession War, I don't see how he could ever lose, unless he goes into a total frenzy. The tie-in with the Kurta clan though... there's room for him to go down with the ship, hopefully literally.
But anyway, there's the other scenario that Hisoka will actually choose to go ahead and do what he promised, and kill a Spider one by one until Chrollo fights him alone in a slightly less skewed match. (I'm not even going to think about that fight because it was the one time in HxH I was disappointed with Togashi's writing decisions. It felt like Hisoka was horribly nerfed compared to every instances we've seen of him fighting. All he had to do was have Chrollo find someone with a gum-dissolving or non-stick power. But no... )
It could be Hisoka really is stalking the Spiders and there will be real cat and mouse game between them until several more are dead. But that fight will surely end up reaching the VIP floor. Just imagine a scene where Kurapika gets into room 404 (that is Tsseried's room number, yes? Or is it 401?), and finds the Phantom Troupe just chilling there with Tserriednick with a dead or wounded Melody... along with the Kurta eyes and his friend's head. That would be... well, he will be having anger issues. I wonder if maybe this is going to be where he dies. The price he pays for Emperor Time is just insane. (Does he have that issue if he's using it on the Spiders though? I thought the original conditions for using Emperor Time's various abilities was focused on the Phantom Troupe. So maybe this is Togashi's opening to saving Kuropika's lifespan? So long as he's got Tserriednick and the Troupe aligned as one general entity to quash, I could see him being able to utilize his powers against them without using up more lifespan. though that only applies to using it against them specifically...)
At any rate, I actually would like to see things more from the Spiders. I could see them going through a brief series of fights with the Mafia, then getting to the VIP sector. Meanwhile, Illumi finds Hisoka. I foresee them interacting before Chrollo or the others find him, somehow.
right now though, the big death flag I'm really sad about is Senritsu. I always liked her. But she's a walking piece of gruesomeness that Tserriednick finds artistic or appealing. He will want her body, skinned or alive... and he loved her powers. It would be JUST like him to have another copy of Devil's Sonata. And he may want her playing it... perhaps he has been aware it does have power. Or maybe he has it but doesn't realize what it is, and she wants it from him. Either way, I don't see her getting out of that room if the 4th Prince doesn't want her to leave... I pray Theta can succeed, somehow, but chances are she's an unsung doomed hero. Should have just shot the man before he... oh wait, nen beast. Right. Damn, but his nen beast is a true guardian. You notice that it is the same as his father's... very protective, and his is the most proactive and efficient so far at doing its damn job. The others are all over the place, literally.
But yes, the plot points I'm expecting most are the Phantom Troupe reaching the VIP floor, probably sooner than we expect, and Senritsu meeting Tserriednick. I doubt she will escape. Narratively there's no point. I just don't see her telling Kuropika that the rest of his clan's remains are being held on display there.
(fun fact: he was the Red power ranger in Ressha Sentai ToQger)
...
. It's the last chapter of the volume after all. Or maybe Tyson's Nen Beast.