I have several x64 SQL 2012 Developer servers with SP2 and CU4/CU5. In your experience, with this SP/CU mix, is the upgrade to 2014 Developer supported ? I can only find information on the supported path from 2012 SP1 to 2014.
From Microsoft BOL 'Supported Version and Edition Upgrades'
SQL Server 2014 supports upgrade from the following versions of SQL Server:
• SQL Server 2005 SP4 or later
• SQL Server 2008 SP3 or later
• SQL Server 2008 R2 SP2 or later
• SQL Server 2012 SP1 or later
So, as you have 'later' than 2012 SP1, then answer is yes.
The actual 'Upgrades from Earlier Versions to SQL Server 2014' section of the linked article just looks like it is out of date and requires addition of 2012 SP2.