According to this MacRumors article
iPhone X production is not expected to even start
until mid October at the earliest so about all you could expect to find at the Apple Store would be a dummy mockup until probably some time in November and then only if you are lucky enough to catch one on the way out the door with a new owner.
My wife informed me she is going to place an iPhone X order as soon as Apple starts accepting them and says I have her permission to order one at the same time. She assumes, of course, I will be paying for both of them. YIKES!