Anyone who follows the Middleware world, and especially the application server market, should have noticed the change on December 1, 2011.
This date was chosen by Oracle to announce the launch of its next generation of Fusion Middleware products, using 12 as the major release number.
One of the first products to be released for the version-12 family along with the launch of the Enterprise Manager 12c — the Java Enterprise Application Server — forms the foundation of Oracle's Fusion Middleware product Oracle WebLogic Server 12c!
Oracle WebLogic Server is already known as Oracle's strategic number one application server for JAVA Enterprise Applications, and is the first which will be at the 12c release. Later on in 2012, other products from the Oracle family, such as the Oracle SOA Suite, will follow.
As you can see, Oracle replaced the g in the release with c. It all had to do with where Oracle put their focus. The g stood for grid computing which Oracle introduced starting from release 10. Oracle's grid computing product group includes (among other things) a database management system (DBMS) and an application server. In addition to supporting grid computing features such as resource sharing and automatic load balancing, 10g products automate many database management tasks. The Real Application Cluster (RAC) component makes it possible to install a database over multiple servers. Oracle has done a lot of effort to get ready for cloud computing, the c appears in the main release.
Oracle also aligned their internal release numbers, where as in 11g it was a bit confusing, for example, Oracle WebLogic 11g R1 PS 4 stood for version 10.3.5, now internal release-number is 12.1.1