The Funimation VA's for the new One Piece dub held a panel at Anime Expo(I think it was AE). In this vid you can hear the voices for some of the characters.

http://youtube.com/watch?v=7RyUyDFRH78

They do it about halfway through.

And in case you didn't know.

Uncut DVDs have all original names, including Zoro, although that won't be on the TV version.

Voice cast:
Luffy: Colleen Clinkenbeard
Zoro: Christopher Sabat
Nami: Luci Christian
Usopp: Sonny Strait
Sanji: Eric Vale
Chopper: Brina Palencia (Nina in FMA)
Robin: Steph Young

All original BGM is used.

Openings will be Yu Yu Hakusho style. Japanese music with new English lyrics (which will probably be close to the Japanese ones, but with differences to make it flow better in English and match the rhythm of the song).

Both versions will be present on the DVD.