Not a clue, but it seems like prototype devices need to be sent for review, rather than manufacturers simply slapping in a controller and adhering to a few specifications, but this is seriously slowing down adoption, and also makes DIY parts impossible to come by.
For example, DATOptic did sell a Thunderbolt to SATA bridge that you could just connect to a SATA device (along with power) for an instant connection. Or you could slap it onto a PCI bracket and pop it in a computer case with a standalone SATA RAID controller to make your own Thunderbolt connected RAID array.
But right before I ordered one they seem to have pulled it, or are at least no longer offering it to consumers.
You likewise can't buy the ATTO Thunderstream 3808E Thunderbolt bridge, only the incredibly expensive boxed version, because they are forced to sell them to OEMs only, who must submit any devices based on the ATTO bridge to Intel (and Apple too, apparently) for review before they can go on sale.
I did however just read here that Intel has now begun a "Thunderbolt Ready" program for motherboard manufacturers to try to improve adoption through the use of PCIe cards either bundled with machines or added by users later on. It's a bit of a weird add-on though as you need a Display Port on your graphics card in order to provide Display Port for the Thunderbolt controller, but I don't see why you'd want to do that instead of just connecting your displays direct, leaving you with more Thunderbolt bandwidth.
