The guys at GSMArena were contacted by a Nokia Rep to clarify about its updates and who gets what.
Nokia Carla is and has always been Belle FP1, Belle FP1 is only coming to the newer Symbian devices 603, 700 and 603 and we will see it out of the box on Nokia 808 Pureview which is scheduled to go on sale starting next months in some countries before globally becoming available (including in the US, according to US Nokia President Chris Weber).
So while these newer Symbian phones get the Belle FP1 update which comes with new set of widgets, improved browser with HTML5 support, Dolby Headphone, new version of Nokia Maps, improved notification bar and multitasking view, and the Microsoft Apps. The update will also increase the clock speed on the Nokia 700 and 701 from 1GHz to 1.3GHz.
The older Symbian devices (1st gen.) N8, E7, C7 and the rest will get a lesser update, an update that has been called Nokia Belle Refresh, no confirmation however on what this update will include, but it is speculated that this update includes the new v8.2 browser and other changes to the OS.
Both Nokia Belle FP1 and Nokia Belle Refresh are scheduled to roll out soon, pretty soon.