XWiki Enterprise 3.5 is a stabilization release that brings many improvements to the Extension Manager, a new macro for displaying documents in a live table and quite a few bug fixes. This is the last major release of the 3.x development cycle (there will still be bugfix releases on the 3.5.x branch, if needed). The next major release is going to be 4.0.
See http://www.xwiki.org/xwiki/bin/ReleaseNotes/ReleaseNotesXWikiEnterprise35 for more details.
See http://jira.xwiki.org/secure/IssueNavigator.jspa?reset=true&jqlQuery=category+in+%28%22Top+Level+Projects%22%29+and+fixVersion+in+%28%22%33.%35%22%29+and+resolution+in+%28%22Fixed%22%29 for more details