Reporting on Engadget, Brad Molen quotes an HTC spokesman:
The Windows Phone 8X by HTC is our signature Windows Phone available at AT&T, T-Mobile and Verizon Wireless in the U.S. With our focus on the Windows Phone 8X by HTC, the Windows Phone 8S is not currently planned for distribution in the U.S. market.
From a practical sense this is an easy call for HTC to make. It's very hard to have a competitive mid-range phone in the US contract market when every handset carries a similar monthly tariff and the upfront cost of a smartphone is expected to be around the $100 mark, with coupons, special offers, and carrier exclusive deals bringing the price even lower. Given those considerations, why would the average consumer go for the HTC 8S over the HTC 8X in-store?
There is an argument that the networks would prefer the 8S due to the lower subsidy requirements, and perhaps we would have seen some different options if the 8S and 8X had both been available at the launch of Windows Phone 8, but that moment has passed. The competitive and unique network market means an American HTC 8S may show up on the smaller carriers, perhaps as a prepay handset, but there's no guarantee.
For the rest of the world, there are still a lot of people waiting on the HTC 8S, and All About Windows Phone will bring you details, news, and a review of the handset as soon as can.