I believe the Server 2012 R2 is still your best bet right now. The reason is migration on infrastructure is not as quick as desktop migrations.
Here the future is Server 2016 but the great thing here is that many of the concepts that you learn from the Server 2012 will undoubtedly serve you for 2016 as well.
I'm hoping others will post and provide some confirmation as well or at least a reason why they believe that private cloud is still the best option! It's always best to hear both side...even when I'm convinced I'm right...it puts it perspective to the entire question.
Edutainer Manager, ACI Learning [ITPRO]
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