Will SolidWorks 2015 files open in previous major releases (i.e. SolidWorks 2014)?
-No, SolidWorks 2015 files are not backwards compatible with previous major releases. The Previous Release Interoperability feature that was introduced in SolidWorks 2013 will NOT be available between SolidWorks 2015 and 2014.
Files will need to be exported as a neutral file format (such as Parasolid) and imported into the previous version. Note that all feature data will be lost.