In the light of Eclipse Platform moving to require Java 11 as a minimum in September  I think we should move Tycho prior to that.
1. It will affect only JVM version runtime at build time. One can freely target older JVMs as it's done in e.g. Eclipse Platform release where build is running on Java 11 but there are bundles targeting down to Java 1.3
2. It will help a number of projects to ensure that additional bundles are in project's target platform and p2 repositories for APIs removed in newer Java versions (xml.*, inject, annotation....)
3. Projects will update their CIs JVMs
4. Message about ecosystem move to Java 11 will get more attention and less people will be surprised in September.
Red Hat Eclipse Team