Movies really don't mean a lot these days unless it is a big box office production. Anyone can make a film. If the movie is not interesting or not well done, then it actually hurts the case, like the ridiculous Treat Williams movie. Public interest is clearly increased during airings of episodes such as Case Closed or Unsolved Mysteries or Expedition Unknown. The Pageview Statistics on Wikipedia will give you a good history of what the interest in the case is.
I put the DB Cooper viewers/researchers into roughly 3 groups:
1. Those who know a lot about the case and are not swayed by the manufactured suspects like Rackstraw or Reca, and who don't believe the media stories on McCoy. Some of this group have their own suspects and will not be swayed into believing anyone else could be a suspect. Most of this group is concerned with facts about the case. If the case were solved today, some of this group would not believe it, some would be happy it was solved, and some would be disappointed because they don't have anything else to live for. Group 1 is almost everyone on the Cooper Forum and on this thread.
2. Those who know a little bit about the case, and have some interest. These are the ones who concern me, because they all seem to fall for the suspects in the media (Rackstraw, Reca, McCoy) and don't do any basic research on the details. They know DB Cooper hijacked a plane, they could probably tell you it was in the 1970s, and that he took a lot of money. However, they do not get into any of the relevant facts such as age, description, personality, etc. They believe what they have been told. If the case was solved today, they would probably believe the new suspect and realize they were wrong to think it was Rackstraw, McCoy, etc. This group likely does not read Dropzone or Cooper Forum, and if they do, they don't post.
3. Those who don't know who DB Cooper is, or if they do, they don't know anything except that he was a hijacker. If the case was solved today, they would read a few snippets about it on the news and never talk about it again.
Group 2 is the target audience to educate about the case.