@Deicide:
Yeah, but most were already convinced that it would be Franky. I was a Paulie supporter initially, but after the Sea Train, I totally jumped to Franky's bandwagon.
Switch Jinbe with Franky, Shirahoshi with Paulie, and the Sea Train with the plaza battle, and there ya go.
Hell, a lot better, IMO. Jinbe is just the calm and collected dude. When he's part of a joke, he usually is the passive part (the serious one who got caught in it due to others' actions). Franky was really funny, and at the same time had very deep interactions with Robin and Usopp. Franky shone even when he was in the background doing his silly poses behind the all-badass Sanji, while Jinbe kind of disappears in the background while the crew is near him.
By "better", I meant what was more meaningful, Franky helping Usopp to accept Merry's fate or Nami lifting Jinbe's guilt off his shoulders? Do you truly think one trumps the other in importance?
Saying that Jinbe hasn't been mugging at every opportunity like Franky is missing his entire character. Take the last page of the last chapter, for example: you have him and Zoro both side by side in the background, not going nuts, not jumping for joy, but looking up smiling and celebrating in their own subdued, macho way. That's just the kind of character he was written as. Besides, in many of the group shots this arc, he's usually had either the first or the last word. And c'mon, if Jinbe was in the foreground all the time he'd block everybody off the panel.
There's have been zero foreshadowing that a fishman was going to join. Neither Luffy nor anyone else in the crew has even stated something like wanting a fishman in the crew. It's the fans who want a fishman in the crew, and some just assume we will have one, but Oda never stated anything like that in the past.
If being a stated desire were a stead-fast requirement, instead of an archeologist we'd have zombies.
And yet there was a flashback, a dream, his interactions with the crew, him having his own fight and helping the others in arc's climax and the knowledge that Luffy wanted a shipwright. Think about it, if Luffy didn't want a shipwright, they'd not try to convince Franky otherwise, and Franky would remain in Water 7.
If he didn't want a shipwright, the Merry would have sunk and they'd all be dead. The End.
In seriousness, out of what you just said does Jinbe NOT have? A flashback? Interactions with the crew? Having a fight (shared, I'll remind you, like Brook)? Helping the others in the arc's climax? As for the dream problem, read on.
Franky had a lot more going for him than just the cover with him among the crew and saying "Mugiwara Pirates". Aside from posing together with the crew, there's nothing in-story or in-character indicating (right now) that Jinbe's going to join.
The fact that so far he has no reason to go with Luffy. Everything about this man so far has been about protecting Fishman Island. He so far has no dream whatsoever that would require him to hop into a pirate crew again. He so far has nothing to gain by joining the crew. Even "his" flashback failed to flesh out any possible motivations.
What does Jinbe has going for him? A cover and some panels with him posing with the crew.
His exposure in this arc makes him likely to join, but in-story we have been given no reasons for him to become the nineth person.
While I think he will end up joining because of this exposure, I still take it with a grain of salt, and it's no wonder a lot of people are still unconvinced.
You're probably astounded every time you see there's actually a secret message when you use those red lenses.
! 
I've pointed out many times that Jinbe HAS shown in the flashback to be deeply thinking about Tiger and Otohime's ideologies and which is better. If his dream is, for example, "I want to find which path is better," there you'll have it. Chekhov's gun is in there somewhere, so don't be surprised when it's blasted off right in your face.
And to imagine we went through 7 chapters of flashback for no other reason than background; that would have Skypiea's beat by a landslide, that's for sure.