I usually try my best to ignore "coupling" talks, especially when it comes to something fictional but One Piece always seemed to be an exception for me.
The most obvious, will-definitely-end-up-together-someday couple is Usopp and Kaya. I enjoy the fact that the two are thousand of miles apart. If she would've join the crew, sappy romance scenes would've gotten in the way of the funny. And Oda can not have that!
They will meet again, Usopp will tell her all about his wild adventures across the grand line, she'll be a well establish Doctor, he'll be a brave warrior of the sea, he'll knock her up and leave, and she'll completly understand because he's a pirate. Like father like son, eh?
Then there's another most-likely couple, Nami and Luffy. Hell, they're piratically act like married couple during most episodes.He's a goof, she's always serious, he'll complain about something, and she'll yell at him or hit him, or both. I find it amazing how much Nami is able to put up with Luffy, I would've strangled him a long time ago. Eiichiro Oda will most likely will keep these two from becoming more than just friends. Why? "Because screw you! I refuse to fall for your expectations. I'm not going to give you what you want! No matter how obvious it is! There in love with adventure, ass."
A really, really detest LuffyxHancock coupling and I have strange feeling it will most likely will happen. Oda Eiichirō is going to make Luffy EXACTLY like Goku by all means necessary. Boa Hancock proves it. I know, I know, One Piece and and DB are two peas in one pod, but I don't want to watch DB, again! Hancock loves Luffy dearly and wants to marry him and he doesn't got a clue…Gee that sounds like someone we know doesn't it?
When they do get hitched I hope her personality doesn't pull a 180 like Chichi's. From Adorably sweet but tough to an insufferable bitch. (Although Chichi did grow on me, and I love her now)
As for the rest of the crew well... I'm sure they'll find themselves a that special someone later on in life. Hopefully not anytime soon. I do enjoy the Straw Hat's platonic love they have for each other. It's nice to watch an anime that focus more on adventure and friendship than sappy romances.
Oh, and I know this will probably never happen but I'll love to see Robin and Franky get together. True the manga and anime gave us zero evidence that these two dig each other but I like to think they do. But that's just the girly fan in me talking.
"They're in love with adventure, ass."
I lol'd. But I agree with ya ;)