For those not tracking the Mesa mailing list, there's been a continual stream of new patches arriving for Mesa that ultimately work towards this GL3 goal. Intel developers and others (namely the VMware developers and other independent contributors) adding support for new OpenGL extensions, work towards GLSL 1.30 compliance, or cleaning up parts of Mesa to facilitate future support. E.g. just earlier this week a patch series arrived for adding interpolation qualifier support for i965 as needed by GLSL 1.30 and lots of other work.
The GL3 documentation in Mesa Git states that what's still missing from OpenGL 3.0 support in Mesa is the full GL Shading Language (GLSL) 1.30 support, completing non-normalized integer textures / frame-buffer formats, transform feedback, GLX support for sRGB frame-buffer formats, 1D/2D texture arrays for Gallium3D, depth format cube textures, and GLX_ARB_create_context, which in turn requires GLX 1.4 support.
Of more detail, however, is the FD.O DRI work queue that was created by Intel. It offers up a lot more details about the OpenGL 3.0 state, including each particular task, who is assigned to work on it, and an estimated number of days for completion. The priority of the work item is also listed, any dependencies, and notes for the item.
A lot of work is being done towards OpenGL 3.0, but it looks like it still may be a close call if OpenGL 3.0 / GLSL 1.30 will be ready by the end of the calendar year. In quickly scanning through the Wiki list, Dan McCabe, Ian Romanick, and Chad Versace each have around 40 (or more) days of work left, among other developers having assigned work items too. If counting the normal business days and factoring in upcoming winter holidays, it will be a close call to see that list cleared out before year's end.
When talking about the OpenGL 3.0 before year's end target with Ian at XDC2011, he mentioned that he would consider delaying the Mesa 7.12/8.0 release a bit if there isn't full support before year's end but is close. Hopefully that would still be the case, especially if Mesa is to continue with six-month releases, otherwise OpenGL 3.0 support would not officially be here until next summer and past the launch of Intel Ivy Bridge hardware and out of reach for Ubuntu 12.04, Fedora 17, etc.