For many purposes, including the ones the OP mentioned, flash memory and and traditional hard drives are more practical. If I had a crapload of downloaded shows and movies, I would leave them on the system or move them to a home theater PC with a couple of 1 TB hard drives. Thats much easier than burning a crapload of discs, no matter how cheap they may become. Its also much easier for viewing later. Blu-rays take forever to load up, but watching directly off a hard drive or even streaming is close to instant.
I dont really like it, but realistically the blu-ray format is probably the last physical medium we will ever see. With the MPAA and RIAA creating such a fear and hatred of piracy, I think eventually most movies and music will only be available as streaming or downloaded data. You can either rent it, or pay to keep it on your home computer or personal media player. I'm not saying it will happen this year or next year, but eventually I think it will be the norm.
/conspiracy rant