Blizzard has posted the schedule this week for testing of the new bosses in Icecrown Citadel on the patch 3.3 PTR. Here's what Slorkuz on the EU forums says is going down:
October 21 at 7PM EDT / 4PM PDT - Festergut
October 22 at 7PM EDT / 4PM PDT - Icecrown Gunship Battle
October 22 at 19:30 CEST - Icecrown Gunship Battle
As always, these schedules and everything else on the PTR is subject to change at a moment's notice. You can find short descriptions of what we know about the bosses after the break.
Patch 3.3 is the last major patch of Wrath of the Lich King. With the new Icecrown Citadel 5-man dungeons and 10/25-man raid arriving soon, patch 3.3 will deal the final blow to the Arthas. WoW.com's Guide to Patch 3.3 will keep you updated with all the latest patch news.