Key Lime Pie, prediction from a developers perspective
Aaron is a key developer for Paranoid Android. This is his take on what KLP will bring, based partly on observations of Googles staging branches which already contain some of KLP's future codebase.
I thought it's curious that Jean Baptiste Queoru, the head of the AOSP, chimes in - though it might not mean much. Anyway, these are interesting points.
From the commits on aosp master I can tell you it will use gcc 4.7 and will utilize c functions (memcpy, memmov etc) designed for the target architecture (a9,a15,etc) providing a nice speed increase.
I can also say that root will be significantly harder to achieve( requiring a huge oem screw up) on non-nexus devices due to seLinux being enabled, which make giving the su binary permissions much more difficult.
Regarding babel or whatever the unified messaging service is called. It won't be the service of your dreams, due to licensing. Talk messenger and hangouts are all closed source applications whole sms is open source and often replaced by oems. Google can not combing a closed source application with an open source one it just can't happen. What they can do is provide a open source application with plug in support like they did with the maps api and the swipe keyboard. This would explain some of the Google what's app rumours as they could have been trying to work on a android what's app plug in. The plug in model has its own issues but would be the ideal solution but is unlikely. What I'm predicting based on no facts what so ever is just a single application for talk messenger and hangouts not the end all be all but still better.
And just for giggles I think a Google plus will be required for sign in on the K release