It does seem like that spread is indicating some sort of tournament setup. It looks like the select screen for a fighting game or something.
So, lets go ALL the way with it! I'm gonna predict how I see these matchups playing out over the course of the rest of the story.
If I had to guess the matchups and results, personally I would go with:
Dragon v Garling-They are looking right at each other. Plus, the fight makes sense. The leader of the Revolutionaries fighting against the "top cop" of the Celestial Dragons.
=Result: Hmm...I'm tempted to say it's a double knockout. But, that's less fun. So, I think Dragon wins the fight. If only because I kind of want to see Luffy meet his dad once before he dies. Just for the comedy. Then again, I'd like to see Shanks face off against Garling, too. But, we can get what we need between Garling and Shanks in a flashback. So, Dragon wins.
Sabo v Akainu-They mirror each other on the spread pretty well. Plus, again, the matchup makes sense. The Hero of the Revolution versus the Dog of the Government. I could even see this fight taking place at the same time as the Dragon v Garling fight.
=Result: While it would have been nice for Luffy to take out Akainu to avenge Ace, I think Sabo works just as well. Sabo was Ace's brother too, after all. Plus, this kind of functions as a "rematch" between the Flame and Lava Fruit users. I think Sabo manages to pull out a win here, giving us some closure for Ace.
Koby v Imu-This matchup feels the most unlikely. But, that does seem to be what the mirror of the spread is indicating. And, it can KIND of make sense if you think about it. Koby represents the ideals of the Marines, and Imu represents the corruption of the Marines. Imu needs to be defeated somehow in order to have any hope of reforming the Marines as a organization, later.
=Result: Oh, Imu wins. Easily. It's WAY too early in the story for Imu to go down to what is, at the end of the day, a secondary character. Luffy or Vivi will likely be the only people who could knock some sense into Imu. Koby doesn't have a chance. But, I don't think Koby will die. Instead, I think it'd be more interesting if Imu brainwashes Koby and sends him out to fight Luffy. They've kind of teased a fight between Luffy and Koby since the beginning of the manga. So, having him get brainwashed into becoming Imu's "Champion" kind of makes sense.
Aokiji/Kuzan v Senior Silhouette Sr-Which just leaves this matchup as the last on the bottom row, by default. To be honest, since we don't know who the Mystery Man is yet, it's hard to say if this is a good matchup or not. But, frankly, Aokiji's kind of the odd one out here, anyway. It'd make sense to take him out early, to hype up the new mystery guy. I will say, if the Mystery Man does turn out to be The Man Marked By Flames, it'd make sense for Blackbeard to send Kuzan to find him, to get that final Road Poneglyph for himself.
=Result: The Shadow King wins. Kuzan is just going to get Worfed to hype this new guy up. A shame, but Kuzan just doesn't really have the drive or reason to try and get the One Piece for himself.
Which just leaves the Yonko. And I'm not sure if we're supposed to "read" this as a "mirror" (meaning Shanks v Buggy) or if we're supposed to be reading it as "pages" (meaning Shanks v Luffy). The thing is, if it's a "mirror" that means Luffy's fighting Blackbeard next. And I think it's a little too early to do that.
So, personally, I'm going with:
Luffy v Shanks-I think it just makes sense to have the Shanks fight be next. Shanks was right around the Elbaf area. I think it makes more sense to find out what's going on with Shanks and dive more into his backstory before we get too deep into the Final War. This is as good as a opportunity as we're going to get.
=Result: Oh, Luffy's gonna win. No way does he get taken out here and now, if this is the matchup. But, maybe Shanks becomes a ally after the fight. It might not even be a traditional fight. It might end up being a variation on a Davy Back Fight. We'll see how this goes. But, I do think it makes sense for Luffy to fight Shanks at some point in the story. And now's as good a time as any really.
Buggy v Blackbeard-Which leaves us with...this matchup, by default. Honestly, the matchup kind of makes sense. I could see Blackbeard being VERY interested in Buggy's Chop Fruit or Crocodile's Sand Fruit. But, I'm gonna be real, Buggy doesn't stand a chance in a traditional fight against Blackbeard. I feel like Luffy and Blackbeard need to have a fight at some point in the story, so he's not going to lose here. I could see Buggy running away and ending the fight that way. But...here's a idea. What if Blackbeard decides he wants to join Cross Guild, too? I could see him seeing value in being part of this entity. It'd be a interesting swerve. And it would give Buggy time to plot a way to stab Blackbeard in the back, eventually.
=Result: One way or another, Blackbeard will win. A lot like with Luffy, it's too early for him to leave the story. But, the same is true for Buggy, too. So, I think they'll both survive to fight again, later. How is another question.
So, that leaves us with Dragon, Sabo, Imu, Mystery Man, Luffy, and Blackbeard for the next round.
So, let's keep this tournament going until the end! My guesses for the second round matchups are:
Luffy v The Phantom Blot-I think Luffy and this guy eventually have to meet. If only to finally find out who he is. So, I'm going to say Luffy's going to end up fighting this guy, eventually. If only to get that final Road Poneglyph he needs that this guy likely has.
=Result: Main character syndrome for the win! Luffy wins, no doubt. Although, I will say, if Koby did get brainwashed before this would be the time for him to show up and interrupt the fight. So, that Luffy and our Mystery Man have to team up against him.
Imu v Dragon-If Dragon was fighting Garling beforehand, it would make sense if Imu shows up after Garling fails. Then we have the head of the Revolution fighting the Ruler of the World. The New Order versus the Old Guard. It works.
=Result: Oh, Dragon's gonna get curb-stomped. Again, Imu probably has to either interact with Luffy or Vivi before being defeated. Dragon will be used to hype up Imu. (Then again, since BOTH of these characters have done nothing in this entire story, maybe it'd be a draw)
Sabo v Blackbeard-Honestly, I could see Blackbeard going up against either Sabo or Dragon equally. They both have Devil Fruits that he'd probably wants. But, I'm leaning towards this fight, if only because of Ace's history with Blackbeard, meaning this is a rematch of sorts. And Blackbeard has expressed interest in stealing the Flame Fruit before in Dressrossa. And I could even see Blackbeard doing this to try to get on Imu's good side. Trying to join up with the World Government.
=Result: Blackbeard wins, if only for the drama. But, I don't think Sabo dies here. This gives Luffy a chance to save Sabo in a way he failed to save Ace, before.
Which leaves our finalists as: Luffy, Imu, and Blackbeard. (With Buggy probably plotting something from the sidelines). And you know what? That feels about right. I don't really know how the final fight will go, but having those 3 (or 4) as the last ones standing feels right. I don't know if there's a battle royale between all of them, or if some of them will ally with others. Maybe Blackbeard tricks everyone and becomes a massive Demon or something. It could go a lot of ways. Although, Luffy teaming up with Buggy to fight against Blackbeard and Imu would be kind of neat, now that I think about it.
Result: Luffy will almost undoubtedly win the whole thing. But, Buggy will likely take the credit for it. Luffy becomes the True King of the Pirates. But, Buggy takes Imu's place as Ruler of the World (while being watched like a hawk by Dragon and Sabo, making him miserable the entire time).