Beginning of 2013 I published a post about how to migrate Virtual Machines from a 2008 R2 Failover Cluster to a 2012 Failover Cluster.
Today, answering a Forum Question in Technet I looked back at that post:
All that has changed in that process is the naming of one Button. Instead of “Migrate Roles” it’s now “Copy Cluster Roles”.
Therefore I can say that the manual is as well valid for migrations towards 2012 R2.
Of course every environment is unique (you may use SMB Storage, etc.), therefore take care and test the scenario before migrating your productive VMs.