Theoretically this should be possible with the help of exporter and importer, but you would need to try yourself which is the last version of exporter that works with 2.5.
Otherwise you can upgrade to newest Joomla and Seblod without setting a new site, for Seblod you would need to do it in few steps and upgrade to the last one that works with 2.5. first, then upgrade Joomla, then Seblod again. This has been described multiple times on this forum before, so use site search or search with Google to find those posts.