From Tamron:
We appreciate your continuous patronage for supporting Tamron products.
In regards our new introduction, 17-28mm F/2.8 Di III RXD (Model A046), which is scheduled to be released on Thursday, July 25, 2019, we are receiving orders more than anticipated. We regret to inform that production planned for the launch are falling short to fulfill all the inquiries received. Please be informed that there is a chance not all inquiries can be fulfilled after the launch date.
We sincerely apologize for all the inconvenience that this may cause to our customers, including our stakeholders, as well.
It is anticipated that delivery to some customers who have already ordered the product might be made some time after the release date. In addition, for those who are planning to place an order soon, because we deliver sequentially, it may take time for the product to be delivered.
We are making our every effort to deliver the products at the earliest possible stage. Your understanding and patience will be greatly appreciated.
B&H has the Tamron 17-28mm F/2.8 Di III RXD Lens available for preorder.