With this open API and NVIDIA's implementation of it working out well, other Linux drivers are looking to pick-up VDPAU support too -- especially considering its adoption and is designed around modern HD video playback needs. Intel has been considering VDPAU support, S3 Graphics supposedly supports it with their Chrome 500 driver, and we could seem some form of VDPAU surface within Gallium3D in the future. There is also a VDPAU back-end to VA-API.
In an effort to help the adoption of VDPAU by those outside of NVIDIA, last month they published a standalone VDPAU library that was distributed independently of their proprietary Linux graphics driver. This afternoon, NVIDIA's Aaron Plattner has now put in a pull request of a Git tree that would allow DRI2 drivers to support VDPAU by adding name registration support to the X server for this video API. These patches plus others submitted today allow allow choosing the VDPAU back-end implementation on a per-screen basis, in the event of multiple VDPAU-supportive drivers, so that libvdpau knows actually what is being used.
This isn't particularly exciting news today, but will allow for a better VDPAU ecosystem outside of just NVIDIA's binary driver. The X Server pull request of DRI2-VDPAU can be found on the xorg-devel mailing list.