I was going to mention the same as @teefers. There was a rather concerning email a few days ago from Bombich, the reputable company behind Carbon Copy Cloner, warning users of nasty issues that still persist in Big Sur.
These aren’t issues Bombich could fix - they were problems rooted deep in Big Sur that only Apple have the ability to fix. Critical things relating to complicated matters (like the underlying file system) that could cause catastrophic problems.
Not to sound alarmist, but anybody who is not a developer would do well to stay well away from Big Sur for the first few releases. Wait until all the horror-stories have died down on the Apple support forums before considering the update. By which time, Realmac and other companies may have more information to share.
Realistically Big Sur isn’t going to provide any significant benefit to the average RapidWeaver user. For example, your websites aren’t suddenly going to publish faster or achieve any better ranking on Google!