guys that were on the 350Z prototype project as well as some of the consultants who added their input to the project, the exact same questions. Mostly got...(1) we wanted to keep it as close to the real feel of a Z as possilbe...and keep it as close to a true sports car as possible. (2) the designs were originally intended just for a slick top version, we thought about sunroof and moonroofs but opted for the hardtop for the first couple of years anyways. We don't know what the future will hold though. (3) We have plans for a convertible but no T-tops version in the future.
This is just some of the answers I got. So I don't see one in the future plans....but who knows.