Details of the features and work items under each 3GPP Release are kept in the corresponding, on-line, list of features and study items.
A 3GPP description document - Overview of 3GPP Release 11 is available on-line, giving a high-level view of the features that are included in the Release.
Some Background on Release 11
A presentation delivered in June 2013, Identified the advances made in Release 11
Functional freeze date including stable protocols: March 2013 (...what does this mean?)