If past history is anything to use to predict the future, then it is pretty likely that Apple is getting ready to refresh its line of Thunderbolt monitors. Traditionally, before Apple launches a refreshed line of products, supply dries up at third-party retailers and then the Apple store.
Amazon, MacMall, and J&R are all out of stock, according to AppleInsider. Furthermore, the Thunderbolt displays have typically used the same, or similar, technology as the iMac line of computers. The iMacs recently underwent a redesign, and the rumor says that the Thunderbolt monitors will likely receive a similar update.
"Think of the Thunderbolt display as an iMac minus the computing hardware," Djuric, from iFixit, explained.
However, they may not use the same technology, since the iMacs are still heavily constrained, mainly due to a difficult to construct screen. One estimate places it at only 100,000 displays produced between LG and Apple per month.