According to Daily Tech Sun is going to bring out a new NAS line replacing the existing 5000 family. The latest member of that family, the 5320, was launched on May 2nd. Existing 5000 users should be able to upgrade to the new NAS range.
Sun may move its NAS line upwards and provide much greater capacity and performance headroom. It may decide to use serial-attached SCSI (SAS) drive technology and it may cluster NAS systems together for greater performance and reliability. Think BlueArc and Isilon and Montilio performance levels perhaps? Also Sun may be thinking about NAS virtualisation.