Since I haven't seen anyone mentioning this on here (or I missed it), I just got an e-mail from Sonnet saying that their long awaited "echo express pro chassis" is available for pre-order, and will be shipping on the 8th of june. Price is $799. They say it's compatible with the Red Rocket card.
As far as I know it's the first Thunderbolt PCIe extension box that becomes available. Finally !
I ordered one, I hope I won't have to wait too long before it gets to France... ;)