Public Domain Day 2014: The fight for the public domain is on now

I am generally in favor of reduced copyright terms, as a consumer of these works, but the thought has crossed my mind, that authors may be motivated, to some extent, by the idea that they are leaving a long-term financial legacy.

I come from an extended family that once had substantial commercial real-estate holdings, mostly bought by my great-grandfather, and my grandfather and his brothers, with the explicit intention that these properties would help to support multiple generations of descendents . Most of them were lost, but even now, I derive a small income from a share in one of the properties, that I am grateful for, since I apply it for the benefit of my own children.

Although the real-estate/IP analogy does break down at some point, should authors of works not have the right to ensure that their works benefit their granchildren, and great-grandchildren? Does this help to motivate at least some of them? These are not rhetorical questions, and it would be interesting to see what the answer is.

I challenge you to prove that making movies which are based on public domain content does either.

This is rarely a "Science" debate and more often an economics debate.

Which is better? Wizard of Oz in the public domain so Disney can make movies with out paying a royalty? or Mickey Mouse not in the public domain so you can't make movies about him?