A notice has appeared on the Pokemon Global Link website notifying its readers that the Global Link service for Pokemon Black, Pokemon White, Pokemon Black 2, and Pokemon White 2 will be closing completely beginning on January 14, 2014.
This is because of the next generation Pokemon games, Pokemon X and Pokemon Y. According to the notice, a new Global Link will be available for the new Pokemon video games. Certain achievements and records by B/W/B2/W2 players will be possible to transfer over to the new Global Link for Pokemon X and Pokemon Y, however, those players will be required to register for the new Global Link service with their existing user name.
Source : Pokemon Global Link.