Zikula Core 1.5.1 and 2.0.1 are now available. More details can be found on the GitHub release pages:
The 1.5.x series will be provided with bugfixes in parallel to the 2.0.x series. This means all bugfixes will be included into 1.5.x as well as 2.0.x. The core developers intend to release future point releases simultaneously, too. New features will not be available until Zikula 2.1.0 though.