Blizzard announced Wrath Classic Patch 3.4.3 will soon become available for testing along with Icecrown Citadel on August 29.

Wrath Classic Phase 4 will soon be up on the PTR. Specifically, the Icecrown Citadel raid will be available for playtesting on Tuesday, August 29 at 2:00 p.m. PDT.

(Source)

We will soon open a PTR for testing Wrath of the Lich King Classic version 3.4.3, the patch that includes Icecrown Citadel.

We intend to open the raid for initial public testing on Tuesday, August 29 at 2:00 p.m. PDT.

The first raid test will likely close after three days.

Please note that this schedule could change with little or no notice, should circumstances arise.