Today, Karl Berry published details of the release plan of TeX Live 2013. This comprehensive TeX and LaTeX system is available for Windows, Mac OS X, Linux and other Unix systems. While its packages are constantly updated, there's currently an annual release cycle for the main distribution.
The milestones for 2013 are:
March 27: The sources were committed, building began.
April 8: The net installer tlnet and Tex Live 2012 will be frozen, start of the pretest phase, CTAN updates continue there.
May 20: Final build completely frozen, which means no more updates except on the final documentation.