I don’t have any inside information, but I would be shocked if you can’t buy this at Best Buy or any of the other large electronics chains. It’s not going to be limited to Microsoft stores only any more than iPads are.
That said, the Microsoft stores are great, so if you do have one near you definitely check it out.
A cynic might say MS doesn't want end users to unfavorably compare the Surface to real devices side-by-side.
Counting on Best Buy to be around for very much longer is a dream