As a disclaimer – any change out of stock components is likely to be warranty voiding if careful attention to original power draw/wattage specs are not observed. We will be doing testing on this upgrade path for sure though.

The video cards appear to be at least swappable in terms of what Apple offers. Would be very surprised if the different Apple cards couldn’t be swapped and this absolutely leaves the door open to future video card upgrades by one means or another…

The processors are socketed and assuming EFI isn’t locking certain config options, paying attention to the maximum power draw of Apple offered options – the processors should be another upgradable piece of the equation.

And – the PCIe SSD was possibilities as well. it’s got some proprietary aspects, but we do hope to overcome this regardless and then that will be an option.

And of course – the memory is upgradable. Currently we are offering the same up to 64GB as Apple, but are testing a 128GB possibility.
http://eshop.macsales.com/shop/memory/Mac-Pro-Memory

And that’s about it – but that does cover all that’s inside and kudos to Apple for the opportunity there in. This system is unbelievably fast out of the gate, it’s impressive – and when it is time to need faster – the potential to do so appears to be clear and present. That all said, based on the stock 2009-2012 Mac Pros we see on the market – seems many forget what they can do to those systems too. Most really don’t need a new Mac Pro – they’ve not scratched the surface of what their current beast can do. :)