This is the interview from US PlayStation blog E3 coverage
The speaker are Herman and Matius from Guerrilla Games Amsterdam the people behind Killzone franchise
https://www.youtube.com/watch?v=tmJdRluiMnk
Some key points from the Live coverage :
1. It's an open world action rpg
2. The games have been developed for 4,5 years
3. They Start the project with a small team of 20, The reason is because the main team busy with Shadowfall
4. The footage they showed us on E3 was still on pre Alpha
5. The concept and earlier build was made using Killzone PS3 engine then after Shadowfall enigine is finish they move to the new engine
6. The Girls is the main character and her names is Aloy, age around 20's and she is a machine hunter on her tribe (it's remind me of a movie 10.000 BC actually )
7. World setting is on earth 1000 years after post apocalypse
8. The world has been dominated by machine like mechanical prehistoric and exotic animal.
9. The concept is primitive against advance technology species
10. The games combat mechanic will involve strategies ( maybe like DarkSouls or Bloodborn)
11. By defeating the machine the character will able to take some part of the machine to use as an item, weapon, or a resources to make a new weapon
12. They also express their feeling on how they have been keep the secret about the games even from their family and able to surprise them on E3.
13. Why they use Horizon as the title also reflecting on how this game will be a new horizon for their studios
My thought for this games, I think the games will be incredible from many aspect including graphic and also they have been working with the Fallout Las Vegas story designer and also have been working with the guy behind The Witcher 3 quest designer. I cannot wait to play the games 
also i am put some videos of the trailer and some picture
Also ther is another gameplay detail from engadget http://www.engadget.com/2015/06/17/horizon-zero-dawn-first-demo/
"Aloy is special. She's a master craftswoman and an agile hunter"
"There are specific types of robot animals: Watchers guard the herd and send out a screech if they see a threat, while Grazers travel in groups and carry glowing green canisters on their backs (these cans are hugely important to Aloy's society and, in the demo, she is on a mission to collect them)"
"Guerrilla Games breaks down some numbers for this gigantic, angry animal: It's 80 feet long by 30 feet tall (roughly the size of an adult blue whale); it has 93 destructive elements along its body, all of which Aloy can shoot to reveal weak points; and it has 12 attacks, including a tail swipe and long-range projectiles "
