To make a long story short, Symfony now manages its releases through a time-based model. If you want to learn more about the Symfony release process, or about the first Symfony Long Term Support release, or about the release date for next version of Symfony, please take a minute to read the new process. You are also going to learn when we will start working on Symfony 3!
The full details also include a timeline they've projected for the upcoming 2.x versions of the framework, right up to the 3.0 release. The goal of the process is to provide transparency and predictability to the Symfony frmework's releases with 6 month releases and and open plan presented to the community up front.