Therefore we rather go for evolution. Tough Rough plan:
Analyse and design. Prepare the list of all incompatible changes that we need to do in ConnId2.
Modify the interfaces by applying all the incompatible changes. Modify the implementation as well (if possible). Do not add new functionality yet. Just change the interfaces in such a way that any changes that follows can be made in a compatible manner.
Stabilize the functionality.
Release ConnId 2.0.0.
Add more functionality. In small steps. With compatible interface changes.
Goto step 5.