As previously mentioned, most of the interview is from E3, but here's a somewhat liberal summary anyway:
When Final Fantasy originally transitioned to 3D, a good portion of the dynamic scenes had to be pre-rendered. As time advanced and hardware changed, however, scenes that previously had to be pre-rendered can now be displayed in real time, allowing for control over the player character. For example, the Leviathan scene in the E3 trailer - according to Nomura - scenes such as this previously would have been pre-rendered, but now it can be played in real time.
The concept Nomura created for the battle system is to be as seamless as possible including the ability to switch between actions and characters at a moment's notice. Each character together with Noctis is very unique and they'll work together to take advantage of each one's special abilities. Actions such as these would have also been pre-rendered in the past, but are now displayed in real time - such as the scene where Prompto steps up to cover for our wayward Prince.
Because the game is action based, Nomura says that the focus of battles is speed and to cause the enemies to react as much as possible. Both enemies and party members will move around the field while the battle situation changes at a moment's notice. This gives the game a sense of realism and is where Nomura believes XV differs from your typical FF game. FFXV will however maintain its similarities to the older titles by including the visualization of Hit Points on screen - like when an enemy or ally incurs damage and numbers show up on screen. The team decided to keep those elements in, otherwise they wouldn't feel that it was "Final Fantasy." With action and on-screen numbers present, Nomura believes there is no other action game currently presenting itself this way.
FFXV's story is derived from the foundation that created both Final Fantasy XIII and Type-0 which takes its roots from the Fabula Nova Crystallis mythology penned by series writer Kazushige Nojima. Despite those connections, the world itself is its own original concept that has a more modern feel. The game's story is quite simple as it centers around heroes who must recover a stolen crystal from enemies, but it also focuses on the relationships between the various characters that typically define a Final Fantasy style plot.
The game's theme is a "fantasy based on reality" with the concept of its world similar to our own - that said, Nomura says that one of the larger points of XV is the fantasy that develops in the world. Trying to realize that concept before the advent of the PS4 had proved quite difficult for the team. As a developer, Nomura believes the most important part of a hardware is its memory and the more you have the more the impossible becomes possible. With more data allowed to reside in the memory, disc read frequency can be reduced and creating larger worlds becomes possible as well. Memory also accounts for the ability to render things in real time. Because there are so many characters in motion during battles with many weapons that can be permanently loaded - the synergy between FFXV and the PS4 is very good.
Following E3, Nomura had a talk with his staff about the video in which the Behemoth appeared to face Noctis and company. He thought the character's expressions were great but for the monsters he still wants to usher in some improvements. From now on, he wants to create as much detail as possible.
As reported on several times since E3, Nomura is thinking about pairing the use of mobile devices with the PS4 title, since in today's era it's often hard to sit still in front of a TV. Nomura wants players to continue to experience the world of FFXV when they're on the go. While it's been a considerable time since Versus XIII was originally announced, Nomura recognizes that every has high expectations for his title. The staff will do their best to live up to those expectations, so naturally we're made to look forward to their efforts.