The latest version is 11.5.1.2266 which you can download using LiveUpdate, but the version of WinPE remains at V2. There are no plans to offer any updates until such a time as the long awaiting GSS 3.0 is released (assuming it ever happens).
Many users have created their own WinPE 3.1 boot solutions, and there is nothing to stop you doing that yourself, but there are no instructions or procedures for integrating V3.x into Ghost Solution Suite.