Yep. At most Oda would go into the pirate group that destroyed Nami's village, rather than Nami's biological parents. But I doubt he even does that. Nami, Ussop and Chopper's backstories were pretty complete from the get go.
The ones with gaps in their backstories was always Luffy, Robin, Sanji and Brook. I doubt he ever goes into detail about anyone else.
Robin's backstory is pretty complete by now. Well as complete as its going to get.