Google has published a gentle reminder for Android developers on its Android dev blog today. Company wants developers to move to Action Bar from the traditional menu button in their Android apps.
As company is trying to stop relying on hardware buttons with the support for on-screen buttons in ICS, it wants developers to stop relying on the whole menu button concept. According to company, you can easily change the code of your app to bring an action bar for devices running Android 3.0+ and keep the menu button options for older devices.
You can read the full post for all the nitty-gritties.