Right, two dual core processors is technically considered a quad processor machine. But I don't think the G5s are going to go dual core. If anything the G6 (in like 2008) will debut as a dual core chip.
But MOSR is talking about 4 physical processors.
There isn't even room for that in the G5, look at the size of the current heat sinks. The whole enclosure would be heat sinks, no room for one optical drive, let alone two like people want.