The following MSDN reference http://msdn.microsoft.com/en-us/library/ms143393%28v=sql.120%29.aspx says
SQL Server 2014 supports upgrade from the following versions of SQL Server:
- SQL Server 2008 SP3 or later
- SQL Server 2008 R2 SP2 or later
- SQL Server 2012 SP1 or later
However, in our testing, it is possible to upgrade from SQL 2005 SP4 to SQL 2014. There are no messages or detection errors when doing so. Will the final release of SQL 2014 support upgrading from SQL 2005 directly or will there be detection added to the installation to prevent it?