It seems that the latest release shipped in Fedora is 1.1.0 while the latest upstream release is 1.1.1: http://sourceforge.net/projects/stixfonts/files/Current%20Release/ Also, note that STIX 2.0.0 is in development and will probably be released soon: http://www.stixfonts.com/
So one year later, it seems STIX 2 is really going to happen soon: "STIX Version 2.0.0 Release Date Announcement The STIpub companies are pleased to announce that STIX version 2.0.0 will be released on December 1, 2016. Version 2.0.0 will focus on providing a greatly improved text portion of the font that will meet the high standards expected by scientific and technical publishing professionals and researchers. In addition, the math portion of the font will be refined, improving the font's internal consistency and compatibility with various math typesetting systems. The completed STIX 2.0.0 fonts will provide a single, unified solution for all aspects of technical typesetting. Development of STIX version 2.0.0 is being performed under a contract with renowned typeface developer Tiro Typeworks. This site was last updated on 02 November 2016."
*** This bug has been marked as a duplicate of bug 1400602 ***