Thunderbolt is basically a 4-lane PCI-E breakout.
Thunderbolt enclosures, once they exist (< 60 days), will meet your needs.
However, keep in mind, the limit is always going to be SATA unless you're going down the FusionIO route. As someone who does deal with racks of SSDs in SANs (mostly EMC Clariion) and FusionIO at some customer sites, I can safely say that Thunderbolt will do everything you ever need.
And if it doesn't, there are Thunderbolt-FCAL HBAs coming, so whatever, connect to an actual SAN.