The last public update on the VA-API G45 state was in February when it was said that it was still being worked on, nearly a year after its intended availability. Last week though at the Linux Foundation Collaboration Summit I asked Keith Packard about the G45 VA-API state. He basically said that he's seen some form of it internally but didn't express much interest in it, which sounded like it would basically never arrive.
After a user now cited my relayed comments by Keith on the mailing list, Intel's Zou Nanhai has provided new comments. In this message he says, "We are still working on that. Though due to resource limitation, it will be a little slow. But I am fully sure G45 support will be done in Q2 2011."
Intel tends to deliver their quarterly Linux driver package at the end of each quarter (though for example, now into Q2, we haven't seen the Q1'2011 package yet but it's just days a way) that means around the end of June or July we should see G45 VA-API support. Updates to the Linux kernel DRM and VA-API library (libva) will be needed. The patches thus would likely be landing in the Linux 2.6.40 and 2.6.41 kernels.
When we have more information, we'll pass it along.