Should I update from Joomla! 2.5 to 3.x?
From Joomla! Documentation
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In most cases, probably not. Joomla 2.5 will continue be supported until December 31st of 2014 and you can update directly to Joomla 3 once it’s tried-and-tested thoroughly by other users. You can even wait until Joomla 3.5 which will be released in March 2014 and still get a direct upgrade. The only reason you should update is if you need Joomla 3’s features or want to be on the leading edge.