This is a recent post I missed (thanks for the pointer Julius) from the Remote Desktop Services Team (formally known as Terminal Services).
Basically with Windows Server 2008 R2 Hyper-V “We conducted our testing using both non-SLAT and SLAT hardware and found that SLAT enabled processors increased the number of sessions by a factor of 1.6x to 2.5x compared to non-SLAT processors.”
Hyper-V R2 supports Second Level Address Translation (SLAT), which uses new features on today’s CPUs to improve VM performance while reducing processing load on the Windows Hypervisor and new Hyper-V VMs will also consume less power by virtue of the new Core Parking feature implemented into Windows Server 2008 R2.
Some more detail on SLAT can be found here
This possibly increases your likelihood of being able to virtualise the RDS workload – as always testing is recommended.