For those who haven't run across soft-releases before, this is the last step before the final release. Because things haven't been finalized yet, some packages may change between now and the release. It is not recommended to use soft-releases in production.
As noted on Plone 5.2rc2 soft-released a new version of plone.app.layout was released between 5.2rc2 and 5.2rc3, and it breaks the way to build the global navigation menu, so be careful when upgrading your site if you have customized the global menu for some reason.
Products.Archetypes should definitely be updated to 1.16.1 that I just released, otherwise Plone with Archetypes does not start up. For background, see issue I created last week: https://github.com/plone/Products.Archetypes/issues/130