Not sure if RSS is fully valid XML, but you can use this technique to make this happen by outputting usingSQL FOR XML, or using a Script Transformation: http://consultingblogs.emc.com/jamiethomson/archive/2006/07/11/SSIS_3A00_-Output-a-file-as-a-csv-or-an-XML-file.aspx
Or http://sqlblog.com/blogs/jamie_thomson/archive/2010/02/27/outputting-data-to-an-xml-file-ssis-video-nugget.aspx
Arthur My Blog