As one of their own spokesperson said:
We’re discontinuing the Apple Thunderbolt Display. It will be available through Apple.com, Apple’s retail stores and Apple Authorized Resellers while supplies last. There are a number of great third-party options available for Mac users.
Maybe it is also pointing towards a refresh and many of us wish so and some of the many reasons why Apple is doing this cause Thunderbolts are not capable of displaying 5K content and even fails in P3 color gamut which is now a trend been introduced with the arrival of the iMac.
The interesting point that is tickling our mind right now is why Apple is making us shop around maybe of drying out their stock before figuring out a refresh,well may happen true.