IMO there will be plenty of stock soon. I don't believe the RT was a flop. Sales are growing and as more people buy it and tell others the demand will continue to grow. Most of the time it's difficut for a new product to be overwhelmingly successful. Many wait for v2.
There are many reasons that the units could be in short supply. I am not convinced that there were only a few units per store because MS was being cautious. From the news thread on this subject.
Would everybody have been happier if MS had said "Ok guys we don't have enough of these made right now, so we are going to push the release date back a month that way there will be plenty available for everybody to buy on day one"? Of course people would have thrown fits if that was done. Short of hitting the exact number per store (if even possible form a manufacturing supply standpoint) or very slightly more than required MS would probably have caught flak from somewhere about over supply or under supply. What counts now is how frequently the shipments come to fill the demand. Right now it has only been 3 days since release.