I have an Android application that uses the well known Strategies for Legacy Applications. It is build with the Android SDK 2.0 with manifest settings minSdkVersion="3" (API 1.5) and targetSdkVersion="5" (2.0). Question1: Since maxSdkVersion is not specified, the application should be installable and compatable with newly released Android versions 2.01 and 2.1 correct? At this point in time, I am not planning any enhancements that will use any new API features. Question2: is there any value in rebuilding the application with Android SDK 2.1? Question3: If so, should targetSdkVersion be changed from 5 (API 2.0) to 7 (API 2.1)?
Question1: Since maxSdkVersion is not specified, the application should be installable and compatable with newly released Android versions 2.01 and 2.1 correct?
correct.
Question2: is there any value in rebuilding the application with Android SDK 2.1?
not really, if you're not planning on using anything new.
Question3: If so, should targetSdkVersion be changed from 5 (API 2.0) to 7 (API 2.1)?
in general, targetSdkVersion should be the newest version you've tested your application on:
http://developer.android.com/guide/topics/manifest/uses-sdk-element.html#target
来源：https://stackoverflow.com/questions/2076150/should-a-legacy-android-application-be-rebuilt-using-sdk-2-1