Would definitely be a touching scene. I mean, sure, Romance doesn't have a necessary place in One Piece, but it's not like it would completely kill the series to just have Luffy and Nami have even a family like moment. :P
Might be a "strong world" moment. Seeing as they look like they are dressed from that, and from what i hear (movie spoiler alert) Nami is kidnapped and sends a letter telling the gang that the guy who took her is too strong... luffy doesn't read the rest, but you find out that it says, later, that she asks them to please come save her anyhow? So maybe this is them reuniting! Maybe? Who knows... but this was adorable and I love it so!