We are often asked about what cables to run in-wall, or in ceiling, raceway, etc to a projector or other video or audio device(s) in order to "future proof" the installation. Closing up a wall or ceiling is usually a pretty final act and having cables for any future necessary connections already installed is paramount.
Several years ago, having numerous 75 ohm cables installed to the necessary local would support all the necessary forms of Component video with analog and digital audio. Six of them would be fine to support Component video, digital multichannel audio and stereo analog audio.
HDMI changed all of that. Running an HDMI cable could support digital video and audio. You have to test before installation and assure that the cable will work at the length you need with the resolutions you may need now and in the future.
So what about the future? With HDMI continually changing its requirements for cables you probably need the latest, amplified and equalized cables to offer support for 1080p, high resolution audio and possibly available formats coming in the future. While HDMI will be a great solution for a number of years, since there is no sure way to know about where the future lies, HDMI at its best, is possibly a temporary solution, albeit a pretty nice one, and certainly the best currently to use.
Adding Cat5e/Cat6 Cables or Fiber optic cables to the installation is as close as you can be at this point to a "future proof" solution. You don't have to use them now. Just have them in the wall for future possible use. Cat5e or Cat6 is particularly cheap to add. You should add several cables, depending on what the possible usage may be. Running four or five CAT5e/6 cables will cover most any video and audio requirements that the future will bring, using external baluns or converters. The more you run, the more flexibility you will have for the future formats, converters and Baluns. Running two cables will offer a lot of options for video or audio separately. Even two connections may be enough in the future for high resolution audio and video in coming formats.
The conclusion? Cat5e/Cat6 is definitely worthy of considering along with HDMI for inwall solutions, for now and in the future. Fiber is more expensive to have installed, and the devices which take advantage of it are generally more expensive, but it is capable of great data bandwidths. If you are only running audio, or digital audio, baluns using Cat5e/Cat6 are a great way to go.
Cat5 for Audio and Video
Fiber Optic and other DVI and HDMI extension