While rumours abound about the release date for the Ulduar patch, it was confirmed by Slorkuz (a Blizzard Europe employee) that Ulduar testing continues this week. From the post below it makes it clear that it should not be launching this week, since testing is scheduled until Wednesday, and by the looks of it may not launch next week either. Since trash mobs are just being added in now, it seems unlikely that they will be tested before next week, but anything could happen.
Here's the current schedule for Ulduar PTR testing:
On the North American test realms:
Flame Leviathan - Tuesday Night, March 24, starting at 7pm EDT/4pm PDT.
Hodir (Hard Mode) - Wednesday Night, March 25, starting at 7pm EDT/4pm PDT.
On the European test realms:
Flame Leviathan - Tuesday Night, March 24 at 19:00 CET.
General Vezax (Hard Mode) - Wednesday Night, March 25 at 19:00 CET.
Emalon the Storm Watcher is also available to be tested in the Vault of Archavon depending on PTR Wintergrasp status. Test Patchwerks will also be available on Wednesday.
For Hard Mode testing, Shirts of Uber will be available on Ursula McWeaksauce to help simulate a raid having obtained Ulduar gear. Check the entrance area of Ulduar for the vendor.
This schedule could change at a moment's notice due to server, bug, or patch status. I'll try to keep everyone informed as much as possible. Ulduar and the bosses to be tested will remain also open a variable length of time. How long they stay open depends upon a host of factors including designer availability, bug status, etc.
We're very interested in seeing combat logs and parses for all raid testing on the PTR.
Quick Ulduar FAQ:
Q) Where's all the trash?
A) Trash has now been completed, and players will see the trash associated with each boss during their tests.
Q) Where's the loot?
A) All loot should be present.
Q) What about achievements?
A) Should all be complete now. As always, please report any bugs.
You can find the thread in the Blizzard forums here.