Every good franchise loses value. Of course it was popular at first and lost publicity as it died down. I am a bug fan, but am not oblivious to its dying fandom. I will continue to see the movies and even re-read the book, but all major brands eventually fizzle away.
I never jumped on the band wagon fully but I have watched the movies with the exception of the one that just came out. I thought about going to see it but overall I think I'm just going to wait for Redbox. I like the concept, but I've just seen way too much marketing for this.
The first movie was big and the second even bigger. The third and fourth movies will out do the first half easily. People love the characters and find things in them to identify with. They will keep going back to them over and over to see when they go and who they become.
No I do not think that the hunger games franchise is losing steam. They are a very popular franchise and series in the books as well as the movies. The newest movie as just came out and now people are anxious to see the second part of the newest movie.