Terraria Community Forums

I thought it was due to 1.2 having a set release date, at which they couldn't finish it completely, hence the reason they're unobtainable.

"As many of you know we decided to pull several of the mechanics and features from the Lunar Update and do them in a smaller update to minimize the wait for a patch. Now that this is out of the way we will be putting our full attention on the Lunar. Lazure has already been hard at work creating assets for the event and Crowno has a pretty awesome idea for the final boss of the event."