This is pretty brilliant:
“[The] new xMac Pro Server is a 4U rack-mountable enclosure that holds a 2013 Mac Pro, includes three standard PCI Express expansion slots that hook up to the Mac Pro’s Thunderbolt ports, and has enough extra room leftover to fit two 5.25-inch rack peripherals (examples include tape drives or SSDs used for backup purposes).”
The same company also makes a 1U rack mount for a Mac Mini that-
“uses the Mini’s Thunderbolt port to add support for up to two external PCI Express expansion cards.”
Seems to me a great solution if you're looking to upgrade to a new Mac that doesn't come with PCI card slots - video/audio pros come immediately to mind. ProTools HD users with existing PCIe Core/Accel cards wouldn't have to trade in for a Thunderbolt Native interface. Seems like a great idea to me.
See the products on Sonnet's website:
http://www.sonnettech.com/product/xmacproserver.html
http://www.sonnettech.com/product/xmacminiserver.html