From 50MB to 4GB. Android applications have been limited to a maximum size of 50MB. Yesterday Google raised the Android app size limit to 4GB. The size of your APK file will still be limited to 50MB . This is good news for the developers, each app can have two expansion files, each one up to 2GB, in whatever format the developer choose. Google through Android Market will host the files to save the developers the hassle and cost of hosting the files.
For the Users, they will be able to see the total size of the app and all of the downloads before they install/purchase.
Source android-developers.blogspot.com :