Different from Honeycomb which is tablet only Android OS, news from Android Developer's Blog reveal that the new Android OS, Ice-cream Sandwich will be running on all screen size. Honeycomb app's developer that has design their apps to run on large screen have to do some changes to the apps since Android apps are forward compatible. At this moment, the before mention developers has only 2 choices which is to prevent installation for smaller screen or to support smaller screen with the same APK.Official Android Developer's Blogger state that they prefer the later options.
Author's note: It is common sense that Honeycomb developers will have to take the effort to upgrade their apps so that it would be compatible on all new device running on Ice-cream Sandwich, else there are limiting their apps to the vast users.This might not be a very good news for developers(if you are an Android apps developer, this news probably wouldn't be your 1st source) but this is definitely something exciting for the users. Hope that when the Honeycomb apps are compatible with smaller screen, they will make it compatible with older Android OS too?
Source: http://android-developers.blogspot.com/