f My u3a uses Beacon.  Will SiteWorks replace Beacon? 

Beacon and SiteBuilder have separate functions. The focus on the SiteWorks project is to migrate SiteBuilder sites to WordPress with the features available matching SiteBuilder as closely as possible. u3as will need to continue to maintain some groups related information in Beacon and some in SiteWorks, just as they currently do with SiteBuilder. 

While nothing official has been decided there is demand and a desire for integration with Beacon so expect to see announcements when the next development phase of SiteWorks is planned.