Normally, Mesa 7.8.1 would not be released for a couple months until Mesa 7.9.0 is ready. The first point release usually comes when the next major release is ready and just carries various bug-fixes atop the older code-base. With Mesa 7.8, however, that clean-up release looks like it will be Mesa 7.8.2.
Mesa 7.8.1 is coming today as it was discovered that the glxext header file contains incorrect values against the Khronos OpenGL specification -- specifically for GLX_BUFFER_SWAP_COMPLETE_INTEL_MASK. Ian Romanick will now be pulling the latest glxext.h file into Mesa and then releasing it as Mesa 7.8.1.
This release of Mesa 7.8.1 should occur today as stated by his emergency email message. No other changes are expected for Mesa 7.8.1.