More precisely, do we want to drop anything 4.x deprecated, or do we want to drop support in trunk for upgrading from 3.x ? And are we ready to commit now to saying let trunk be 5.0 ?
Our SemVer versioning rules, being operator rather than user facing, state that these compatibility concerns are the requirements that warrant a major version jump. (Because we are otherwise always to be strict with providing compatibility.) A separate question: do we want our major version to jump simply because we drop support for an older JDK? My opinion is that we shouldn't, as this would churn our version numbers and leave us less in control of (minimising) the upgrade paths we force our users to go through. And that's not to say new JDKs won't force other changes that themselves justify the jump.
