Previewed at WWDC, launching in the fall.
PowerMac G5 Updates - March 23rd?
According to their information, the new machines will come in at the following specs:
Dual 1.8GHz G5, 256MB DDR400, 80GB HD, GeForce 5200 Ultra
Dual 2.2GHz G5, 512MB DDR400, 160GB HD, Radeon 9600
Dual 2.4GHz G5, 512MB DDR400, 160GB HD, Radeon 9600
MacPlus.org does not frequently publish rumors, but has published an accurate release date in the past.