Technically speaking, Amazon Echo Auto is still by invitation only and there has been no release date mentioned. Many people have been receiving invites. However, there are many more people who want an Echo Auto and have signed up, but have yet to receive an invitation. There is also no status indication of whether you will ever receive an invite.
But a Reddit user pointed out an Amazon system glitch that allows you to purchase Echo Auto without being invited. See the conversation thread.
You are able to purchase Echo Auto by either adding an Echo Auto bundle or by adding the product to your wishlist first. If in your wishlist, you can add it to your cart. Once in your cart, you’re able to checkout and purchase one. Wow!