The Kepler release cycle is focused on performance enhancments and functional improvements in the core framework and well as significant functional improvements to Xcore. All activies are tracked via this bugzilla report.
The 2.9 release ams to be binary compatible with the 2.8 release, except for the Xcore framework, which is primarily targeted for end-users rather downstream frameworks. The Xcore language itself maintains source compability with the previous release.
Java 1.5 compatibility is ensured. Eclipse 3.5 through 4.x is supported. Xcore relies on the Kepler version of Xtext.