Solution
The NI HSS PXIe-6592 can be used with all four ports at the same time and there is no technical limitation around it. The default example provides only the starting point and the same code can be replicated for additional two ports. Of course, there is some work required towards CLIP modification which will also need experience on Xilinx Vivado Design Suite.
We currently do not have any NI official example which covers the 4 ports use case. However,
this NI community example uses all 4 ports for Tri-Mode ethernet and should be a good starting point.