Polybase was first made available in Analytics Platform System in March 2013, and then in SQL Server 2016. The announcement at the PASS Summit was that by preview early next year, in addition to Hadoop and Azure blob storage, PolyBase will support Teradata, Oracle, SQL Server, and MongoDB in SQL Server 2016. And the Azure Data Lake Store will be supported in Azure SQL Data Warehouse PolyBase.
With SQL Server 2016, you can create a cluster of SQL Server instances to process large data sets from external data sources in a scale-out fashion for better query performance (see PolyBase scale-out groups):
I’m excited for the future of Polybase and looking forward to vNext and vNext + 1 (for the stuff which they can’t possibly get done in time for vNext).