Why in the home?
Because they can my friend!
Think of the extras that could be put on a disc of that capacity. Lower compression for video, higher bitrate for audio.
Heck, a disc of that size would be George Lucas's dream! He could market 30 or so versions of each Star Wars film, in HD, WITH all kinds of extras and sell them on a single disc!
Imagine having access to an entire library of films. Yes, cost would be a consideration, but on older films that have gone into public domain, a couple hundred movies could be "shoveled" onto a disc of that size!
How about the data possibilities? What about the possibility of maintaining your own personal library of literary works?
Yeah it'll come, but I wouldn't hold my breath. There is too much money to be made on the HD/BluRay products (if marketed correctly).