Since One Piece is such a long series, is still going on without any signs of stopping in Japan, and Viz graphic novel realeases are still way too slow (even after they changed the realease dates from every 4 months to every 3 months), I have a feeling that Viz will soon pull One Piece from the Shonen Jump magazine and make One Piece a GN only series from there on in.
Viz did do it for 2 of their other series. They took the Boo saga of DBZ out of the magazine and made it a GN only series because EVERYONE has seen DBZ on TV already, the same thing for Yugioh, everyone had seen the Duelist Kingdom and Battle City arcs, so it didn't really make sense to have it in the magazine with 2-3 chapters realeased a month.
I just have this feeling that after Viz finishes up the Arlong arc and Louge Town and the Straw Hats finally enter the Grand Line, that One Piece will be pulled from the magazine and realeased either monthly or bi-monthly in GN form starting with volume 13 or so. American fans that don't download manga or episodes have already been given a rather shitty preview of what the Grand Line brings (through the atrocity that is the 4Kids dub) and since One Piece is a 39 volume+ series, it's clear that one GN realease every 3 months isn't enough.
I just have some weird feeling that Viz will do just that.