With Oculus' now rather unsavoury connections I really hope documentaries like these will be made available in some format that's easily portable to other VR devices.
As for the plans to support VR at all: Great. I hope this is going to work out well. I can't think of many recordings more deserving of immersive visual experience than those of Sir David Attenborough.
Facebook is a controlled ecosystem and based on their previous behaviour they will try to maintain as much internally as possible - which will mean keeping as much media exclusive for Facebook as possible.
I agree. All the more reason then to try to release things like these documentaries in a more general format as well; alternatively just in the more general format with an adaptation layer to support the Rift.
I'd hate to see vendor lock-in for gems like these, especially if it's a company like Facebook they're being locked in to.
