Having just deployed 2 server 2012 clusters in my environment, I was surprised to find an email from MS in my inbox this morning about Server 2012R2. On the virtualization side they have a couple of key improvements:
VHD/VHDX Deduplication
Live Migration Compression
Live Migrations with remote direct memory access
Improved support for Linux guests
Not necessarily related to virtualization but still cool, the 'storage spaces' feature released in 2012 will include support for 'storage tiering', which traditionally has only been available on enterprise class SANs.
http://www.microsoft.com/en-us/server-cloud/windows-server/windows-server-2012-r2.aspx?WT.mc_id=Newsletter_TechnetFlash_TechEd_General_EN_US&loc=zTS3z&prod=zWSz&tech=zOttechz&prog=zOTprogz&type=znewsz&media=zOTmediaz&country=zUSz