"National Geographic has confirmed that they will only be releasing high definition titles on the Blu-ray format. The decision to go format exclusive comes after Warner Brothers, the company which distributes their content, decided to go Blu-ray exclusive earlier this month. While no official press release will be issued on the subject by National Geographic, all future releases will fall under this new policy.
The first title to fall under this new policy will be the April release of 'Sharkwater' which should get an officially announced soon. National Geographic is the latest studio to switch to Blu-ray exclusivity, and the third to do so under the Warner umbrella (joining ranks with New Line and HBO). The only Warner holdout left is BBC, who remains format neutral and will continue to release on both formats."