Tigole had the following to say this morning about the PTR realms.

We're taking the PTR's down today. Hopefully, we'll have them up sometime tomorrow. Once they are up, we ask that we get extensive testing on the Gothik the Harvester event. We know that guilds are anxious to see all of the encounters in Naxxramas, but at this point, we need to focus testing where we need it the most.

We will do our best to have people online who can advance your raid directly to the Gothik event.

Thank you, again, for helping us make this dungeon.

You can comment in the thread on the official forums here: Naxxramas Update.