The first- and second-generation devices were codenamed "pancake" and "biscuit" respectively, and the new third-generation device is rumored to have been developed under the codename "donut". Rather than the flat top of the current Echo Dot, it appears that its newer counterpart has a more rounded appearance.
The biggest change, however, is with the addition of what looks to be fabric covering the sides of the device. This is more in keeping with the second-generation Echo and the Google Home Mini (which is a direct competitor to the Echo Dot).
There are still four buttons on the top of the device -- like its predecessor -- that handle volume up/down, mute and action. There appear to be 5 microphones on the top of the new Echo Dot instead of the current 7, but as AFTVnews reports, beamforming tech should allow Amazon to get away with using less hardware.
The new Echo Dot is also slightly larger than before, which brings to its primary reason for its existence: to provide better sound. The sound output on the current Echo Dot is a bit on the tinny side, so any improvement will be much appreciated. However, there's only but so much that Amazon will be able to do with such a small device while maintaining its $49.99 MSRP.
We should note that we usually take such images with a grain of salt, but AFTVnews, which has leaked unreleased Amazon gadgets before, adds, “P.S., Let’s just say I’m confident these images are real.”