For the frameworks version of kdepim we require a libkolab version that builds on frameworks.
Porting to frameworks is mutually exclusive with old kdepimlibs and thus also libcalendaring, at least without significant extra effort and #ifdefs.
This means the porting will result in a libkolab 1.0 that depends on a couple of KDE Framworks and Qt5 and a c++11 compatible compiler (gcc 4.6.2 or so).

Since this will result in a new major version, we should probably take the chance to clean up some of the uglier interfaces (KolabObject).

The only thing I need to know is wether breaking backwards compatibilty is an option, or if there are other alternatives that I did not consider.