To add a bit to dialabrain's comments, this "warning" is letting you know that some app or component that supports that app, may or may not, work with a future release of macOS. Most, if not all application developers typically participate in the Apple Developer's beta program. This give them an opportunity to decide if they want to upgrade their respective apps to be compatible with a future OS release. Furthermore, each work to their own development timelines ... so it may be possible that they may not have an update in time. So, if you have particular apps that you rely on, you may want to hold off upgrading to a major new OS release until such time as that app's developer provides a compatible version.