updated 01:35 pm EST, Thu February 28, 2013
Could hint at update
The Thunderbolt Display is only available in low quantities at Apple resellers, notes AppleInsider. Amazon, J&R, and MacConnection are out of stock, though companies like Best Buy, B&H, and MacMall still have units. Apple's online store continues to have the monitor ready to ship in 24 hours.
Problems with supply started back in January. A persistent shortage may suggest that Apple is letting stock evaporate in advance of a new model, as it regularly does with its products. A new Thunderbolt Display could be engineered to reflect the design of current-generation iMacs, but their unique screen construction has led to production problems, something the company is likely keen to avoid exacerbating.