True, but I suspect that doesn't massively prolong most movies, only big ones that people are passionate about (Star Wars, The Godfather Trilogy, etc).

Just randomly picking... 2004. Top 10 movies from that year, and pulling future media sales predictions out of my ass:

  Shrek 2                                   kids movie, profitable regardless.
  Spider-Man 2                              probably poor
  The Passion of the Christ                 probably poor
  Meet the Fockers                          nobody cares.
  The Incredibles                           kids movie, profitable regardless.
  Harry Potter and the Prisoner of Azkaban  great.
  The Day After Tomorrow                    nobody cares.
  The Bourne Supremacy                      possibly good.
  National Treasure                         nobody cares.
  The Polar Express                         nobody cares.

I mean, I am sure all of these will have future releases on new media. There is no reason not to re-release movies, it is essentially printing money), but will many of them see dramatic sales that will really change how we view the profitability of those movies? Meet the Fockers was a good movie, but nobody is going to give a shit if you re-release it in 3D, 4K resolution, "hyperdisk". Only a few have that potential I think, and it gets more bleak if you stop looking at the top 10.

After the initial burst of home media sales, I just don't see most movies getting anything more than a trickle of revenue. For every movie like Office Space, there are dozens that aren't.