Officially announced today, VMware is extending the availability of the vSphere Enterprise license which was supposed to be retired the end of this year.

From the release to the partner channel:
Customers have provided clear feedback that they want more flexibility in managing their upgrades to vSphere and to Enterprise Plus.  Therefore, VMware is extending availability of VMware vSphere Enterprise beyond the end of 2009.  This will enable our customers to continue to buy vSphere Enterprise in 2010.  Availability of Enterprise will continue as long as customer demand exists.

The current upgrade promotions, Enterprise to Enterprise Plus and Enterprise to Enterprise Plus with the Cisco Nexus 1000V, will end on December 15.

How does the 6-core restriction work for Enterprise?
The Enterprise core entitlement remains at 6-core and is technically enforced in the product.  However, two Enterprise licenses can license one 8, 10, or 12 core processor.