I previously wrote that the 130 nm G5 970 has now been retired. Further evidence to support this is that the current G5 2.0 also shares a motherboard with the G5 2.5, and the machine is recognized as a different one than the original G5 2.0.
If one types "ioreg | egrep Power" in the Terminal, one will see that the current G5 2.0 is called "PowerMac7,3". The previous G5 2.0 was called "PowerMac7,2". Apple's published G5 block diagram also shows a common motherboard for the new G5 2.0 and the G5 2.5.
I'm not aware of all the differences between the previous and current motherboard revisions, but one notable difference is that the HyperTransport speed has now been increased to 4.8 Gbps (vs. 3.2 Gbps in the original Power Mac G5).