From LSP4E perspective, the project already has a patch ready for adoption of 0.9.0 ( https://git.eclipse.org/r/#/c/149444/
). It can be merged as soon as it's 100% sure LSP4J 0.9.0 gets into SimRel. Later -but the sooner the better-, we'll adapt the target platform to reference LSP4J release repository, as LSP4E p2 repo does include some LSP4J artifacts.
SimRel and synchronizing on a release date is actually not very comfortable for LSP4E and family. to ensure we don't ship incorrect versions of LSP4J in LSP4E releases, it means we need LSP4E release build to run against an LSP4J release. This is much simpler if LSP4J release happens soon, whenever it's ready rather than having to wait for a specific date a few days before a major and not moveable deadline to change dependencies and cross fingers that things work in a constrained timing.