It's great thinking about the possibilities that Thunderbolt will one day provide. However, thunderbolt technology for external drives ONLY makes sense with SSD.
So unless SSD prices start dropping dramatically in the very near future, few people are going to take advantage of this technology.
In a few years, It'd be interesting to see what percentage of 2011 thunderbolt-equipped Macs will ever have used that technology. So far, thunderbolt is pretty much a feature that is theoretically awesome but way too overpriced.