The plan is that each major release of Joomla will be supported for over 4 years.
Joomla 2.5 will be supported until December 31st of 2014.
The final version of the 3.x series will be Joomla 3.5 planned for release in March of 2014 with support until the end of 2016.
All of the Joomla 3.x versions will be one-click upgrades performed in the Joomla Update Component.
