Fenix will be the new replacement for Firefox on Android
Mozilla is now working on a new Firefox alternative for the Android platform. The latest version of the Firefox is the last version to receive any major feature for now. After this, you will not get any major feature. The new browser is Fenix.
The latest version of Firefox recently got a feature of preventing websites to play audio/video automatically. Since Mozilla is now working on the new Fenix browser. You will not receive any new feature post-ESR (Extended Support Release) channel. That is after the last major hits the Play Store, and the app is bumped to version 68.1, you will not get any major update/feature.
The last update will come on September 3rd. Until then, the update release will go as planned by Mozilla. For now, Mozilla will continue to support Firefox, unless Fenix is ready to deploy.