While World of Warcraft's Public Test Realm has taken the backseat in favor of the Wrath of the Lich King beta, it doesn't mean Blizzard has totally ignored the test server altogether. The European servers have recently been wiped to make room for the new 3.0 build of the PTR, according to Blizzard poster Tigole.
Tigole also mentioned that some patches were on the PTR for over two months already and should receive some major testing once it goes live. In addition, 3.0.2 will be sure to arrive some time before Wrath of the Lich King 2.0.1, similar to when the pre-Burning Crusade patch was implemented a month before the actual expansion was released.
Since there are still a lot of people trying out the WotLK beta, this means people who want to test out the new updates in the PTR will have a lot of free space on the Realm to do so. Also, Tigole mentioned that none of the classes are done, so anyone willing to sign up for the PTR will be more than welcome.