This weekend the FreeBSD 5.4 Release Schedule was updated to reflect "facts on the ground." The candidate earlier labelled "PRERELEASE" is now noted as "5.4-BETA1", and the comments state:
"First public test release build. Note that the release build name is 5.4-BETA1 but newvers.sh RELEASE name remains 5.4-PRERELEASE. This is because the name BETA often confuses the users who are using the STABLE branch."
"5.4-RC1" is slated for 31 March, but then we read the "First release candidate" is scheduled for 2 April. 5.4 is listed as having a 19 April availability date.
This information is a lot more specific than what I see from most commercial operating systems. :)