It's Nexus Eve Day, and let's be honest, nobody is getting any work done because we're reading all of the exciting news about tomorrow's announcements. Your wish list may already be written and tucked beneath your pillow waiting for St. Matias to give it a look. While we await the big event, Google actually has some of its own official news to share today. As it turns out, Google is raising the maximum apk file size on the Play Store from 50 MB to 100 MB.
— Android Developers (@AndroidDev) September 28, 2015
The change is largely a formality since the file size restriction is an artificial cap. The 50 MB limit was left over from the launch of the Android Market (later renamed to the Play Store).
Back in 2012, Google added a workaround for developers that still required them to keep their app's apk below 50 MB, but allowed them to include up to two "expansion files" (i.e. obb files) that can be as large as 2 GB each. Executable code was to remain in the apk while the obb files were meant for extremely large resources like maps, audio, video, and whatever else couldn't realistically fit into the core app.
The problem with the expansion files is that they're obnoxious to use if an app was only slightly over the limit. Back in the early days of Android, when developers only had to use resources ranging from ldpi to hdpi, it wasn't too hard to keep sizes down. Now that QHD displays have become commonplace on phones and resources in the xxxhdpi bucket are expected, apps have naturally grown larger and push right up against the 50 MB wall pretty easily.
With the new limit in place, developers can build their apps to the size they need to be, rather than cutting corners on resources or pushing a few megabytes of leftovers into expansion files. Keep in mind that this change won't really make apps any larger, it'll just make it less of a hassle for developers to package them. Google has been sending out apks that exceed the 50 MB limit for quite a while, like certain variants of the Chrome for Android web browser which can weigh in at about 70 MB.
According to Google's blog post, this change will also affect the warning message that appears for downloading large apps. It should now only appear when an app requires expansion files and totals more than 100 MB. The developer docs haven't been updated to reflect the changes yet, but they'll surely appear shortly.
- Android Developers Blog