Good point. You can see what we have planned as breaking changes for 3.0 on the planning board:
Most of these look fairly easy to knock out. I'll try and get the issues about removing deprecated code out of the way ASAP. Havard, can you have a look at #1227, which I think is a trivial fix, technically?
The biggest open issue I think is a documentation one: a declaration of what constitutes our public API (#619). This is marked as not backward compatible because it may change the understanding between us and our users of what parts of Rdf4j are considered "public API" wrt semantic versioning.
Of course, apart from these things we also had a lot of general new features and updates on the todo list for 3.0. The more we can fit in the better, but most of those can be shifted to the next minor, if needed - so they don't have to hold up a release.
I'd like to do a few milestone builds before full release, probably at least two. That gives us an opportunity to collect feedback, as well as time to get the formalities (release review, IP log, etc) out of the way.
Cheers,
Jeen