He reminded me there are alternatives, like the AT&T button, but they're larger and more expensive and not rechargeable nor do they have a replaceable battery (though they are LTE-M instead of WiFi).
More importantly, he said they have a manufacturer who's producing a similar but improved device (rechargeable or replaceable) that should be the same price point. These should be available in late March. Why Amazon created a 2+ month gap here is beyond me, but so be it.
On the server side, they are going to continue to support the back-end IoT services and have no plans to deprecate those.