The Weekly Quandry: Irrelevance Through Influence?

I was perusing io9 this morning and found a post by Marc Bernardin on the idea of a Starship Troopers TV show. For the uninitiated, Starship Troopers is Robert Heinlein's 1960 Hugo Award-winning novel about a boy named Juan Rico who joins the military in his futuristic society. The text depicts his entrance into and ascension through the ranks of the armed forces, who are at war with an alien species known as the Klendathu. Bernardin's piece pointed me towards another post on io9 in which Josh Wimmer gives a fantastic breakdown of the novel for anyone who hasn't read it. You can also check out Wikipedia, or just read the book. I strongly encourage the latter because it is an incredible text and nothing like Paul Verhoeven's 1997 "adaptation" (which for the record was also completely awesome in its own way).

Bernardin asks why there has never been a faithful adaptation of Heinlein's novel, particularly as a high-budget television series like the recent Battlestar Galactica reboot. He mentions the fact that the novel has been hugely influential as a major selling point for a new adaptation, arguing that because its products have been so successful (ie Avatar, or just about anything sci-fi that James Cameron has ever done) therefore the progenitor should be a sure thing. I found myself disagreeing with his logic, and thinking that the core elements of Troopers might actually be over saturated in a market so heavily influenced by it. If we've seen aspects of Heinlein's work in everything from Aliens to anime then have we reached the point at which Starship Troopers ceases to be able to bring new ideas to the table?

Which bring me to this week's quandry: is it possible for a text to be so influential as to render itself irrelevant? I don't mean to say that Starship Troopers or texts like it are not worth reading, far from it. But in terms of new cultural products, is there anything else that these kinds of classic texts have left to offer? What is there left to say that hasn't already been addressed in a whole spectrum of mediums?  I use Starship Troopers as my primary example, but there are other texts/films/etc that this question could be asked of, such as I Am Legend (each new adaptation of which continues to further drive this point home) or Neuromancer (which was pretty much done in forever by The Matrix). Is there a point to returning to these classics for their own sake, or have they been rendered irrelevant by their intellectual offspring?

Sound off and let me know.