Meteor City arc for sure.
Outside arc to end the series.
That's all I can think of right now.
But I'd like to see more places explored (Hanzo's homeland of Jappon for instance).
You never know where Togashi is going with all this, Gon himself and the reader may not see what happens in the outside till later. If I had a choice I'd rather the Outside arc happen last. But you are right it does seem like its right around the corner. Only time will tell.
Futurefrog hit the nail on the head give us a Meteor City arc, I want that so much. Something that feels like Yorknew again, flesh out Jairo's character, get Kurapika and the spiders relevant again.
Aside from Outside and Meteor City, maybe an arc that can flesh out other parts of the Hunter world. Like what is marine life like in the Hunter universe? I was pretty intrigued when we met Morel and they mentioned his profession as a Sea hunter. One of my favorite things about NGL was how it all started with some beast Hunting, so maybe an arc all about archeological Hunters? Find out more about civilizations of past in the Hunter universe, that could unravel into something bigger.
I'd also love to see any arc where we can get more of the Hunter Examinee's in their field. Basically I just want to see more types of Hunters doing what they do, and in the process have Gon and Killua find out what kinda Hunters they want to be.
I think Outside is the end game. I think Togashi is playing us for fools and we are getting a Meteor City arc next.
I 100% agree with everything said by Americandream. There is still a lot of other parts of the world I want to see about. I don't think we get Outside until the end if we ever do.
The Dark Continent Arc will be next i think
I'm hoping for a Jairo arc and with the other missing division commanders accounted for (praying mantis and "glutton king" alligator), although I really don't know what kind of story could come from this.
I'd like to see a Kurapika arc with him being hunted by Ryodan members. While everyone knows about Kurapika's weakness, his fifth chain might cover his vulnerability? Nobunaga might be the next to go. Kuroro might hatch a wise plan to take down Kurapika but Hisoka will probably intervene.
Illumi surely can't stand being pushed around by Killua and Alluka. Illumi might confide in someone to help seize Alluka (someone other than Hisoka). I just can't imagine extraordinary characters like Alluka being left lying around in the HXHverse, something will happen to complicate matters (maybe even resulting in Alluka's death?).
Pariston seems to be a part of Beyond's team so we might hear from him much later on. The hybrid eggs are a concern now since they've probably all hatched.
You raise an interesting point about Alluka, her powers is something needs to be resolved. I think that Killua may try and find a way to 'cure' Alluka and Nanika. Maybe splitting them into two different people? I dunno, it's just one of those hanging points that will have to be solved by the end of the series.
I really can't predict what kind of arc Togashi will come up with next, but I'd love for there to be an arc which gets the whole gang back together. I kind of miss seeing the main four together as a group.
I think the most likely thing to happen is probably X-Day, IIRC that's supposed to take place in the next Hunter exam. Since Killua re-took the exam on Greed Island and a lot of time have passed. The probability is high that it will happen once Gon has found a goal for himself. Or maybe Togashi will show us the "hunt" for the 18 missing Hunters, that is something that also needs to be resolved. As for the other points, you guys already mentioned: Outside and Meteor City will take place on a later stage. Due to Jairo raising to power first and then clashing with the Ryodan's.
I would love to get the building blocks/foundation for Meteor City arc, reintroduce the Ryodan to new readers/or returning readers who've forgotten. I totally forgot about the missing Hunters, I wonder if that Lupe guy is alive, I kinda hope he is. I honestly really wanted to see Bushidora's Hatsu thanks Hisoka!
X-Day sounds awesome too. The Chairman election arc opened up a lot of possibilities, its great. I hope that most of the things we want to see get to happen. Though I'm really unsure how they'll resolve all this stuff with Alluka and Illumi.
Why do have feeling that Illumi is going to control Killua eventually?
I definitely want to see consequences or a conclusion to Killua/Illumi/Alluka ordeal. Also maybe see the big old lady Butler fight!
I'd actually rather see it play out different, we had Killua technically being controlled by Illumi for so long with the pin in his head. Though I don't know what else they can do with Illumi, I honestly don't actually feel I know him that well as a character for how important he is in the story.