As of chapter 489 or 490, Luffy finally got a musician to join his group. That musician is Brook, the musical skelton. He came back to life after eating the Second Life Devil Fruit. IF you actually read it, he has a connection to Laboon, the whale they met at the enterance of the grand line.
Now as for the new story arc, the starw hat crew had fished up a mermaid.
I won't go into much detail yet, because I'm not going to spoil everything for you, yet.
-Darknessslayer