We need to update to Windows Server 2012 R2 as soon as possible. The only thing that ties our hands is the lack of Plesk support for it. Can you tell us how long should we wait for the R2 support, in order to plan our upgrade proccess?
I haven't any ETA when 2012 R2 will be supported.
Use supported version of Windows for your Plesk. Then you may migrate to server based on 2012 R2 if it is so important for you.