Google is increasing the maximum APK size in Google Play from 50MB to 100MB. The move comes in response to developers creating apps which offer richer experiences, and helps to avoid the need to download additional data after the initial APK download.
Expansion Files can still be used to allow for apps that exceed the 100MB barrier, but the aim in increasing the base limit is to speed up the installation for users. Now, rather than downloading an app followed by additional updates once the installation is complete, larger apps can now be downloaded and installed in one fell swoop.
The idea is not to encourage the development of bloated apps, but to provide a way to "build higher quality apps and games that users love". The new size limit applies to apps created for Android 4.0 and above.
Google points out to developers that just because the maximum size of apps has been increased, there's no need to use the full quota with every app. The company reminds devs that large apps will take longer to download and may result in large data bills for people. They also take longer to install and use more system resources.