Back in 2015, Sony created the "Sony's Concept for Android" program for the Xperia X. The result was something between a beta program and an alternate ROM that offered a mostly-stock Android experience with fast updates. Unfortunately, Sony has decided to end the program - at least for the Xperia X.
The announcement comes from Sony's InTouch community, which has served as the hub for communication between Concept users and Sony since the program began. According to the Concept Team, the final update will come in early May, possibly being a stable version of the experimental 7.1.2 release.
The post also says that a similar program will eventually become available for the XZ Premium, which as the name implies, is expected to be quite expensive. The post did not say if the Concept program will continue to receive security updates.