With updated documentation in the Mesa tree, here's a look at what's left to be accomplished for the Mesa drivers to catch up with the latest upstream Khronos specifications for OpenGL 3.x and OpenGL 4.x.
The ARB_ES3_compatibility extension as mandated by the desktop OpenGL 4.3 standard is now written off as done within the documentation, thanks to Intel OTC quickly doing OpenGL ES 3.0 support in Mesa, so now the overall list appears as:
GL 3.2:
Core/compatibility profiles DONE
GLSL 1.50 not started
Geometry shaders (GL_ARB_geometry_shader4) partially done (Zack)
BGRA vertex order (GL_ARB_vertex_array_bgra) DONE (i965, r300, r600, swrast)
Base vertex offset(GL_ARB_draw_elements_base_vertex) DONE (i965, r300, r600, swrast)
Frag shader coord (GL_ARB_fragment_coord_conventions) DONE (i965, r300, r600, swrast)
Provoking vertex (GL_ARB_provoking_vertex) DONE (i965, r300, r600, swrast)
Seamless cubemaps (GL_ARB_seamless_cube_map) DONE (i965, r600)
Multisample textures (GL_ARB_texture_multisample) DONE (i965)
Frag depth clamp (GL_ARB_depth_clamp) DONE (i965, r600, swrast)
Fence objects (GL_ARB_sync) DONE (i965, r300, r600, swrast)
GLX_ARB_create_context_profile DONE
GL 3.3:
GLSL 3.30 new features in this version pretty much done
GL_ARB_blend_func_extended DONE (i965, r600, softpipe)
GL_ARB_explicit_attrib_location DONE (i915, i965, r300, r600, swrast)
GL_ARB_occlusion_query2 DONE (i965, r300, r600, swrast)
GL_ARB_sampler_objects DONE (i965, r300, r600)
GL_ARB_shader_bit_encoding DONE
GL_ARB_texture_rgb10_a2ui DONE (i965, r600)
GL_ARB_texture_swizzle DONE (same as EXT version) (i965, r300, r600, swrast)
GL_ARB_timer_query DONE (i965, r600)
GL_ARB_instanced_arrays DONE (i965, r300, r600)
GL_ARB_vertex_type_2_10_10_10_rev DONE (i965, r600)
GL 4.0:
GLSL 4.0 not started
GL_ARB_texture_query_lod not started
GL_ARB_draw_buffers_blend DONE (i965, r600, softpipe)
GL_ARB_draw_indirect not started
GL_ARB_gpu_shader5 not started
GL_ARB_gpu_shader_fp64 not started
GL_ARB_sample_shading not started
GL_ARB_shader_subroutine not started
GL_ARB_tessellation_shader not started
GL_ARB_texture_buffer_object_rgb32 DONE (i965, softpipe)
GL_ARB_texture_cube_map_array DONE (i965, softpipe)
GL_ARB_texture_gather not started
GL_ARB_transform_feedback2 DONE
GL_ARB_transform_feedback3 DONE
GL 4.1:
GLSL 4.1 not started
GL_ARB_ES2_compatibility DONE (i965, r300, r600)
GL_ARB_get_program_binary DONE (0 binary formats)
GL_ARB_separate_shader_objects some infrastructure done
GL_ARB_shader_precision not started
GL_ARB_vertex_attrib_64bit not started
GL_ARB_viewport_array not started
GL 4.2:
GLSL 4.2 not started
GL_ARB_texture_compression_bptc not started
GL_ARB_compressed_texture_pixel_storage not started
GL_ARB_shader_atomic_counters not started
GL_ARB_texture_storage DONE (i965, r300, r600, swrast, gallium)
GL_ARB_transform_feedback_instanced DONE
GL_ARB_base_instance DONE (i965, nv50, nvc0, r600, radeonsi)
GL_ARB_shader_image_load_store not started
GL_ARB_conservative_depth DONE (softpipe)
GL_ARB_shading_language_420pack not started
GL_ARB_internalformat_query DONE (i965, gallium)
GL_ARB_map_buffer_alignment DONE (r300, r600, radeonsi)
GL 4.3:
GLSL 4.3 not started
ARB_arrays_of_arrays not started
ARB_ES3_compatibility DONE (i965)
ARB_clear_buffer_object not started
ARB_compute_shader started (gallium)
ARB_copy_image not started
KHR_debug some work done (ARB_debug_output)
ARB_explicit_uniform_location not started
ARB_fragment_layer_viewport not started
ARB_framebuffer_no_attachments not started
ARB_internalformat_query2 not started
ARB_invalidate_subdata not started
ARB_multi_draw_indirect not started
ARB_program_interface_query not started
ARB_robust_buffer_access_behavior not started
ARB_shader_image_size not started
ARB_shader_storage_buffer_object not started
ARB_stencil_texturing not started
ARB_texture_buffer_range DONE (nv50, nvc0)
ARB_texture_query_levels not started
ARB_texture_storage_multisample not started
ARB_texture_view not started
ARB_vertex_attrib_binding not started
For reaching OpenGL 3.2 compliance, most of what's left is OpenGL Shading Language (GLSL) 1.50 support along with bits of the
geometry shaders enablement. After that, OpenGL 3.3 will quickly come into place.
OpenGL 4.x features though, however, have a lot of work until they'll be found fully implemented in Mesa/Gallium3D... Don't expect them in 2013. It's going to be a long time until OpenGL 4.3 compliance is found in Mesa, which is sad considering the next Khronos OpenGL specification update is right around the corner.