Csound1 makes a valid point: "Why not ask these questions of the manufacturers of enclosures, nobody here has access to their future plans, and Apple do not make external bare enclosures."
Valid though this might be, it seems to me that, as the initiator of the existence of Thunderbolt ports in personal computers, it is at least possible that someone in the extended Apple family might know why there has been such a long delay between putting the ports on Macintosh computers and third-party manufactures starting to build Thunderbolt enclosures. Thus, it is logical to ask the question in this thread, because it is at least possible that at least one person who reads it here, be they Apple employee or not, might know the answer and post it.
However, "knowing why" there has been such a delay and "being willing to say why" are not necessarily the same thing. Let me just take a wild guess here. I posit that there are many, many Apple employees who know exactly what the answer to this question is, but who have been deterred from publicly stating the answer (or, in the current doublespeak of of 21st Century America, they have been "disincetivized," to contort our already contorted version of English one more step).
To say that it is be someone else's product, and that, therefore, we must ask this question on this unnamed entity's website is a cop out. After all, if the products have not yet been built, they are no less Apple's products than anyone else's. And in any case, it is not credible to say that, because Apple does not build it, neither Apple, nor anyone who reads this thread, would know anything about this issue, thus preventing them from even making an educated guess as to the answer.
Let me take one more wild guess here, since no one is willing to say anything more definitive. My wild guess it that, because, at least at the beginning, the number of Thunderbolt devices manufactured will be relatively small, and because the licensing fees that must be paid to Apple and others are relatively large in comparison to the numbers of Thunderbolt products produced, the economies of scale dictate that the strategy of Apple and their third party partners must be to sell only very expensive Thunderbolt products initially, before providing their customers with reasonably priced enclosures that can be populated with competitively priced hard drives or SSDs.
This is a pity. The poor home user takes it in the shorts again. They are sold computers that have been hyped as having a great new technology (Thunderbolt), only to find out after they buy it that, unless they are willing to pay a price that rivals the cost of their computer, they probably will not be able to actually make use of this new technology (Thunderbolt), until after the computer has long since been parked in the attic, gathering dust.
I hope that everything that I have said here is untrue, and that tomorrow I will see an Apple Thunderbolt product (or product of one of Apples' third-part partners) for sale that I can afford to buy. After all, I can't help but think that Steve would never have allowed such a strategy, even if the economies of scale deem such a strategy more economically more feasible than thinking of Apple's customers first.