Very often, developers will open up apps and games for pre-registration. It is primarily to gauge the public's interest in the app, allowing the company to strategize accordingly. A lot of devs even throw in some in-app bonuses for early adaptors. As a result, a lot of people express interest in an app that won't release until several months in the future. It is easy for users to forget about the apps, and that's why a future version of the Google Play Store will automatically download apps that one has pre-registered for.
The upcoming feature was discovered by XDA Developers, who did a deep dive into the Play Store APK. It was found in Google Play Store v18.6.28, which contained several references to functions that would automatically install pre-registered apps and games. Once the or game has been installed successfully, you should get a notification saying, "You pre-registered for this app and it's now installed on your device. Enjoy the app/game!"
Currently, the Play Store relies on a notification that tells a user that their app/game is ready for download. While it is a fairly efficient way of going about it, notifications are easy to miss, especially if you happen to get a lot of them. On the flip side, installing an app without notifying a user might come off as a tad intrusive. An ideal solution lies somewhere in between and we hope that Google has that figured out.
Furthermore, several modern-day are now a few gigabytes in size. A single unsolicited download can wreak havoc on devices that operate on a limited data plan. We're assuming that the Play Store will hold off on downloading the app based on the user's Play Store updates preferences. The best way to go about it would be to create a new section in the Play Store settings for pre-registered apps and let the users fine-tune it according to their preferences.
It will be a while before we see the feature in action, though. The version of the Play Store in question was a beta build, indicating that it still has to go through additional testing before it is deployed en masse.