Joomla 2.5 has reached its end of life on December 10th with the release of version 2.5.28. After that date Joomla! 2.5 will no longer receive any updates. This means that no bugs or security issues will be fixed. Joomla! 2.5 will be unfit for use on live sites.
Per our policy regarding End-Of-Life Joomla! release branches, the current version branches of our software will continue to support Joomla! 2.5. The next version branch of our software will only support the latest version of Joomla! 3. If we're releasing a new version branch of our software less than a month after the Joomla! 2.5 EOL, i.e. before January 10th, 2015, we will support Joomla! 2.5 in this branch of our software. Finally, we have a support cut-off provision: no support for Joomla! 2.5 after April 1st, 2015.
New version branches of our software which do not support Joomla! 2.5 will not be designed to run on Joomla! 2.5 and will not install on Joomla! 2.5. While we do take measures to prevent the update stream from showing them to you as available versions, we understand that a misguided and determined user may try to download and install their ZIP file packages. We do try to prevent that use case as well. In the off-chance they do install despite our provisions, please remember that they will NOT be designed to work in Joomla! 2.5 and could lead to the software or even your site being broken. If this happens we will not provide any support. Simply put, you should not try installing a component not explicitly marked as compatible with your Joomla! version, it will break stuff.
How to upgrade to Joomla! 3
We understand that many of our users are afraid to upgrade from Joomla! 2.5 to 3. In the past upgrading from one major Joomla! branch to another was indeed a difficult task, e.g. from Joomla! 1.0 to 1.5 and from 1.5 to 1.6/1.7/2.5/3.x. But this is all in the past. The Joomla! project has made strides as far as updates to major versions are concerned. Upgrading from Joomla! 2.5 to 3 is virtually a single click process.
We strongly advise our clients to watch the Joomla! 2.5 to 3 video tutorial by Brian Teeman (courtesy of SiteGround) for detailed upgrade instructions.