The vmwgfx DRM driver is needed for its kernel mode-setting support and use by their new Gallium3D driver. This driver targets no actual hardware but rather their SVGA interface that will allow guest operating systems running with VMware virtualization to access the GPU on the host to provide OpenGL acceleration or support in other areas where there is state tracker coverage (OpenVG, OpenGL ES, X11/X.Org, and soon OpenCL). David Airlie, who is also the mainline DRM maintainer, has also got the VMware KMS driver working with QEMU.
As the Gallium3D driver is open-source -- as is much of VMware's other graphics work since acquiring Tungsten Graphics last year -- there should not be much of an issue getting the VMware DRM driver in the mainline kernel, at least compared to VIA's battles and the Intel Poulsbo mess.
The RFC for this vmwgfx work can be found on dri-devel.