CAS 3.4.10 has already been released (maybe later releases since this writing?)
Continued backwards-compatible highly conservative bugfix and security fix releases in this maintenance series
CAS 3.5 Release
Upgrades to core storage mechanisms. Most importantly, the API
Introduction of core Factories for creating tickets
Update to Ticket terminology to support future protocols
Updates to internal code base to support new APIs
Replacement of Jasig License with Apache 2 License
CAS 3.6 Release
Rewrite of Services Management Tool
Extraction of Services Management Tool into its own Web Application
Consideration for Future Protocols
Addition of Registration Tool
New Integration Module between CAS Server -> Management Tool
CAS 3.7 Release
Rewrite of two Core Interfaces: CentralAuthenticationService, AuthenticationManager to support additional use cases. These additional use cases include message passing to users, better throttling, CAPTCHA, integration with password management tools, etc.
Updated UI to take advantage of latest use case additions including message returning
Updated UI to reflect recent UI trends (immediate feedback on validation, etc.)
Enable Advanced Use Cases including Session Id switching per request, etc.
CAS 3.8 Release
Monitoring: JMX, Statistics publishing, support for Nagios, etc.
CAS 3.9 Release
Support for OpenID2. This would be the first test of the new APIs to ensure we can support additional protocols
CAS 4.0 Release
Basic SAML 2 support. "Basic" is defined as the minimal subset of required profiles to actually do something useful
CAS 4.x Releases
Support for additional SAML 2 profiles, additional useful protocols, etc.