Let's discuss the next steps instead of talking about version numbering. If our changes legitimate a 4.0 then we could rename the version afterwards.
I go for a drop of java 5 and 6 in 3.10. It's not a big deal but increases the performance and code qualitity by using some new java features.
In parallel we could try to migrate to another build system. I'm not sure but I think we've to change the packaging and then we should talk again about the upcoming version number.