MythTV 0.23 introduces a new event system, a new Internet video plug-in, new audio code, new themes, updated FFmpeg libraries, and many other changes.
MythTV 0.24 is already in development and its slated to bring a new MythUI OSD (On-Screen Display), a nearly rewritten audio subsystem, Blu-ray disc and disc structure playback, and other performance, usability, and flexibility improvements. The new audio subsystem is to be capable of handling 24 and 32-bit audio and up to eight channels of audio output.
In terms of Blu-ray support within open-source software, the x264 / VLC project has had success working on a Blu-ray encoder, Xine-lib has also been working on Blu-ray support, MPlayer now supports most HD-DVD and Blu-ray codecs, and the format has been a growing focus within the FFmpeg project.
The MythTV 0.23 release announcement can be read on the project's web-site.