B&H has it up, but it isn't available for preorder yet. It's the same story at Adorama and Amazon.

Please remember to support the site when making your 5Ds / 5Ds R preorder. If you sign up to be notified when the preorder is available, I'm not sure the site will receive credit for referring you to the product page for notification at a later date. But once preorders are available, if you click on the "Buy" link from our site (or even navigate to a retailer using our main retailer links), then the site will be supported through your purchase.

Just keep us in mind - Bryan's worked really hard on the preview. :-)