Aside from announcing a price drop for Metal Gear Solid V: Ground Zeroes on PlayStation 4 and Xbox One, Konami made a few additional announcements.
Players who buy Ground Zeroes will receive exclusive downloadable content they can use in The Phantom Pain. This content is described as ‘additional resources for Mother Base’. This DLC will be available in the ‘first batch’ of the retail versions of Ground Zeroes, and for a ‘limited period’ in the digital versions.
As stated earlier, characters rescued in GZ and character skins will also carry over to The Phantom Pain.
Thirdly, Konami also announced the iDroid App. This companion app allows players to connect their smartphones and tablets to the game and use them for various things, such as displaying the map, calling air support and playing cassette tapes.
Here is a part of the official press release:
First, it was revealed that those who purchase METAL GEAR SOLID V: GROUND ZEROES early on will receive exclusive DLC for use within THE PHANTOM PAIN. The DLC will only be available in the first batch of the retail version and for a limited period of time for the digital version. The DLC provides players with additional resources for a Mother Base area that will be available in THE PHANTOM PAIN. Mother Base is introduced during the events of GROUND ZEROES and plays a central role in the forthcoming METAL GEAR SOLID V: THE PHANTOM PAIN. Unlocked through downloadable code, the added staff for Mother Base will give GROUND ZEROES players an edge when they take on THE PHANTOM PAIN.
In addition, anyone that purchases GROUND ZEROES will be able to unlock exclusive content within the game to carry-over to THE PHANTOM PAIN. Prisoners of war and VIPs rescued in GROUND ZEROS will be added to the Mother Base staff in THE PHANTOM PAIN, providing GROUND ZEROES players an early in-game advantage; character skins will also be able to be carried over.
Source: Konami Press Release, via Kotaku, Gamespot