Upgrading a Joomla Website
Lately I have had numerous discussions with customers in regards to upgrading their websites from older versions of Joomla to the newest supported version - Joomla 3.6.4.
Support for Joomla 2.5.28 has now ended and I am recommending that my customers consider upgrading their sites to the supported stable version. Version 3.6.4, is now the stable version, and as a result, security patches will no longer be provided for any older versions of Joomla.
How to Upgrade Your Joomla 2.5.28 Website
Upgrades are a tad time consuming since all non compatible extensions need to be uninstalled and then replaced with compatible extensions after the upgrade.
Also before the upgrade the site's template needs to switched over to a compatible template first, then the old template would need to be uninstalled and replaced with a compatible template for the new version, and re-customized.
My Joomla 2.5 site is working fine, why do I need to upgrade it?
As we are all aware, technology changes very quickly and keeping your website updated is essential to keeping up with everything new. For Example, who knew a few years ago, that mobile phones and tablets would virtually replace desktop viewing of websites?
Today's websites need versatility to handle all types of views, from large screens to tablets to smart phones, and if websites don't have this versatility, they may fall in ranking with search engines.
If a version is no longer supported, it becomes a security risk and becomes attractive to hackers who tend to prey on vulnerable websites.
An upgrade is a great time to change the look of your website and do a little spring cleaning and changes to a website. It is also a great time to review your site's search engine optimization key words and phrases and resubmit website URLS and sitemaps to the major search engines.
Last Official Migration for Joomla
From what I have also read, this will be the last "official upgrade migration" and future upgrades will be a simple button click upgrade. As a result, this would be a great time for to upgrade your older sites.