This new Bochs DRM driver was part of a larger DRM patch-set for QEMU emulated graphics support with small improvements for Cirrus and QXL graphics. When it comes to having KMS/DRM drivers for use by QEMU, there is already the Cirrus KVM/QEMU driver and QXL DRM driver for Red Hat's SPICE protocol.
The basic patches from this six-patch series were merged today for drm-next and going into the Linux 3.13 kernel, but the Bochs driver wasn't accepted. The developer behind this work, Red Hat's Gerd Hoffmann, had said the driver was a work-in-progress and wasn't calling for its mainline inclusion. There also wasn't any major improvements to this standard driver over the past month.
In a mailing list post by DRM subsystem maintainer David Airlie, he said, "I'll try and find some time to look at the bochs driver, though is it really much more than we have with the simple drm layer that David Herrmann is producing?" What David noted as the other alternative is SimpleDRM, which is a generic KMS/DRM driver of sorts and seeks to replace vesafb, efifb, simplefb, and vgafb. SimpleDRM is basically for a single-output single-mode driver driver that's basic yet compliant with the DRM interfaces.
The Bochs DRM driver is just about a mode-setting driver anyhow and what most Linux users dealing with open-source desktop virtualization are really waiting for is 3D/OpenGL support for guest virtual machines, which hopefully will be provided in the months ahead by Virgil 3D for Gallium3D-based guest VM acceleration that will hopefully be able to take on the 3D acceleration provided for years already by VMware's products as well as VM VirtualBox.