Microsoft has confirmed Hyper-V in Windows 8, in its latest blog post.

In building Windows 8 we worked to enable Hyper-V, the machine virtualization technology that has been part of the last 2 releases of Windows Server, to function on the client OS as well. In brief, Hyper-V lets you run more than one 32-bit or 64-bit x86 operating system at the same time on the same computer. Instead of working directly with the computerís hardware, the operating systems run inside of a virtual machine (VM).

Hyper-V enables developers to easily maintain multiple test environments and provides a simple mechanism to quickly switch between these environments without incurring additional hardware costs.