The sarge freeze is now official.
The expected timeline for the release is as follows:
3rd May (Today): Freeze time and security support now available for testing
5-8th May: BSP to bring bug count down from ~85 to ~60/70
15th May: Debian installer finalised
27th May: Zarro RC boogs
30th May: Release
Now that there is official security support for testing you are very much encouraged to test the upgrade path between woody and sarge and report any issues to the BTS.
http://osnews.com/comment.php?news_id=10488
http://www.debianplanet.org/node.php?id=1232
http://lists.debian.org/debian-devel-announce/2005/05/msg00001.html