As far as I know this is NOT the case. For instance, the Supported Configurations webpage for SCOM 2012 R2 shows that for both SQL databases (Operational Database & Operations Manager Data Warehouse) the supported SQL Server versions are: SQL Server SQL 2008 R2 SP1, SQL Server 2008 R2 SP2, SQL Server 2012, SQL Server 2012 SP1.
And this makes sense. Simply because SQL Server 2014 will become General Available in 2014 where as System Center 2012 R2 will be released in Q3/Q4 2013. And until now not a single Microsoft product supported a release of another product which wasn’t GA on the date of its own release.
Will SCOM 2012 R2 ever support SQL Server 2014 as a platform for its SQL databases?
And yes, in the future, when SQL Server 2014 is GA a future update of System Center 2012 R2 will add support for it. But until then, SQL Server 2014 won’t be supported as a platform to host the SQL databases.
How about monitoring SQL Server 2014 with SCOM?
Basically Microsoft delivers within 90 days of the GA date of any Microsoft product the relevant MP for it. The SQL team delivers a good SQL MP and have been on top of things with all other SQL MPs. So personally I expect the related MP to be released pretty soon after SQL Server 2014 becomes GA.