There are no upgrade or backcompatibility issues with the 2.5 series.
Xapian search and indexing: make the search insensitive to
diacritics. You should reindex the sites with
amusewiki-bootstrap-archive --xapian after the upgrade.
Xapian indexing: give more relevance to titles and author
Upgrade forkawesome to final version
Improve translation UI
Improve bookbuilder session loading
Add a max requests to the FCGI process manager
Add new options for federated sites acting as a pure mirror (remove local and vanished files from upstream)
Improve bookcover stock template
When generating and EPUB in the bookbuild, also produce HTML
i18n: tr (updated, thanks to @rojenzaman)