Note: Test realm is now up!
Blizzard Quote [source]
Hey guys, thanks for your posts and, more importantly, your patience!
We are actively working on bringing the PTR back up. It's the first one ever for Diablo III, so it's a little rough around the edges. I'll post back when I have some more info.
The currently goal is to get the PTR back up by the end of today so you guys can check it out before Mists of Pandaria launches.