EA is pursuing a very sound strategy of developing in house engine that its studios can use. After all licensing Unreal engine over and over again doesn't make much sense for such a huge publisher. So Frostbite Engine developed by DICE is soon to become a flagship technology for EA.
Its iteration came with Battlefield 3 and helped to provide beautiful visuals for games such as Need for Speed: The Run, Medal of Honor: Warfighter, Army of Two: The Devil's Cartel or for the yet to be released Command & Conquer strategy.
Now Battlefield 3 itself was a huge success. EA claims that the game sold over eight million copies in the first month so I'd speculate the game sold over ten to twelve million copies to this day (digital sales are not published anyway).
Battlefield 4 is coming with Frostbite 3 - an engine that's already in use for many high profile titles in development. Be it Need for Speed: Rivals, Dragon Age: Inquisition or Plants vs. Zombies: Garden Warfare.
Does the rush to release new BF start to make sense to you now? Battlefield 4 doesn't offer sweeping changes. It's a safe sequel that tries to sell incremental improvements at best. It's hard to imagine that the employees in DICE are truly excited to work on this title. But it comes with a new engine and under well established brand and it will probably sell well.
That sounds a like great way to fund the development of Frostbite 3 for future heavy use in games that are published by EA. After all we're already seeing signs of this.
But what's in it for DICE? Business is always about a great deal of diplomacy and the development of Mirror's Edge 2 doesn't seem like a coincidence. First game was great but also one that underperformed. And it's not surprising. Mirror's Edge has an awesome concept that seems quite niche.
This makes me believe that there was a deal between EA and DICE that encompassed development of Battlefield 4 in modern setting and release in 2013 in exchange for EA's yes to the development of Mirror's Edge 2. Maybe. Or maybe not.