Android Ice Cream Sandwich (ICS) is the upcoming major redefinition of Google’s mobile platform and while we don’t know what it will look like, we already know that ICS will run on all kinds of screen sizes - from small to large and covering everything in between. Thanks to a post on Android Developers, we also have a pretty good idea of how apps will behave in ICS with the biggest change coming to Honeycomb apps which devs are adviced to make compatible with smaller screen sizes in a single APK.
Honeycomb-only app would have to redesign it so it starts supporting smaller screens as well. There’s also the option of preventing installation on smaller screens, but it’s not advisable.Basically, this puts an end to the confusion whether an app would or wouldn’t work on a handset. Since ICS is compatible with both phones and tablets, a developer having a
source: Android Developers