The physical Menu button is an interesting holdout from an earlier age of Android. While Google's devices and those manufacturers that roughly follow Google's guidelines (like Motorola and LG) don't use it, Samsung and a few others do, leaving app developers in a tight spot when it comes to implementing an overflow button. Today a Reddit user found this change to the Action Bar Policy file for KitKat in Google's Git repository.
The gist is that now API-compliant apps will always show the overflow menu button on the action bar at the top of a Holo app, rather than having it appear or disappear depending on whether or not your phone (or tablet, SAMSUNG) has a physical menu key. It's a small change, but it means that the user interface for apps that use the overflow menu button will remain constant across devices rather than shifting based on physical parameters.
Google engineer Adam Powell placed this comment on the change in Git. Because why the Hell not?
Always show overflow buttons on action bars The menu button is not pining, it's passed on! This button is no more! It has ceased to be! It's expired and gone to meet its maker! It's a stiff! Bereft of life, it rests in peace! If you hadn't nailed it to a flagship device it'd be pushing up the daisies! THIS IS AN EX-BUTTON!!
This change should only affect phones or tablets that have been upgraded to KitKat, so at the moment I think only the Google Play Edition devices will see it. Maybe this will finally convince certain manufactures (still looking at you, Samsung) to abandon the hardware menu button. But probably not.