With all the hype and media going on about Batman: Arkham Knight, it's hard to get the information you need. Here's a list of all the important facts, from the extent of the Batmobile's inclusion to whether the game has multiplayer or not.
In case you couldn't gather from the trailer and almost every bit of promotional material, the Batmobile is a big focus of the game. It's built not only as transportation but an extension of Batman. You can glide out of it and it knocks aside any debris in the way. Thugs magically roll out of the way though, so expect no bloodshed regardless of the beastly tank you'll be driving.
There will also be no real civilians to save. This is primarily due to the inclusion of the Batmobile so that you wouldn't accidentally run someone over as Batman. In the story it's explained away by Scarecrow threatening the city with a new lethal fear toxin, so everyone besides Commissioner Gordon's task force, Batman's allies, and Batman vacate the city.
Speaking of the Batmobile, the Riddler is going to be building missions specifically for your new ride in addition to numerous new puzzles and harrowing danger rooms. He's changed his look as well, look more like a deranged car mechanic now.
Almost all the villains are united now in trying to break Batman. While he can pursue them as he pleases, they all will push him to the limit in their own way. As for the sudden change and unity, the power vacuum left by the events of Arkham City has finally given the chance for the villains to realize they would work better as allies. However, old familiar friends will not be the only threats you'll see.
The Arkham Knight in the title is not Batman, but a new character, created by Rocksteady in collaboration with Warner Bros. He wields a pistol with deadly accuracy, but otherwise seems almost like a twisted soldier version of Batman Beyond's Batman. He is the main antagonist, but it's unclear as of this writing where he stands with the other villains. He also carries the distinctive A from the Arkham logo on his chest.
Arkham City will look like a peaceful country side town in comparison to the constantly rioting streets of Gotham. The game is apparently around four times the size of Arkham City. To compensate for this, gliding and mobility have been enhanced and speed is increased overall.
Brawling has been seriously updated as well. Batman can now use environmental takedowns, instant ground takedowns for certain enemies, and use their own weapons as his own (base ball bats, bricks, etc.). The animation system has also been upgraded to allow Batman have a far wider range of motion. Gadgets can all now be used mid-glide as well.
Yes, we finally get to see the face of Oracle, and she will be a far major character than in either previous game. Her clock tower base can be visited by players, and may potentially serve as a secondary Batcave.
Commissioner Gordon has either been retconned to an age closer to Arkham Origins or is now dying his hair. Either way, expect him to look younger than in previous games other than Origins. He will also most likely be playing a far more prominent role.
Judging by the game's first trailer, car combat may very well be a feature, in addition to the already reported Riddler racing challlenges.
Rocksteady has stated this is their final Arkham game. While Warner Bros. Montreal can continue making midquel material between the various core games, the Arkhamverse has a definitive endpoint for Batman. It has been implied they may even go so far as risking killing off Batman.
Despite a small yet active cult following for Origins' multiplayer, Rocksteady has made it clear they will not be featuring multiplayer in Arkham Knight. It's unclear if Warner Bros. Montreal will bring it back in any of their titles.
As has become customary after the Mac/PS3 exclusive Joker DLC for Arkham Asylum, a new alternate playable character is available in Arkham Knight. This time we'll be playing as Harley, who touts four new maps. Also, apparently the Batmobile may be interchangeable judging by the pre-order skin with unique perks from Wal-Mart.