End of support for IOS 15 / MacOS 11 !?

When I just updated the latest Version of the Companion App it showed an information, stating that this will be the last version which supports macOS 11 / IOS 15 /WatchOS8

Unfortunately there is no more information anywhere what this will mean for older devices, which are often used to run the HomeAssistant Dashboard using the Companion App.
Maybe someone can explain the consequences ?