A graph of mentions of "John Keats", "Dan Simmons", "Ode to a Nightingale", "Ode on a Grecian Urn", "The Eve of St. Agnes" since 1800. (It wouldn't let me use more titles)
https://books.google.com/ngrams/graph?content=John+Keats%2CD...
So I guess the Simmons theory would see an upswing after 1989? I don't see any increase in the mentions of his poems. The name "John Keats" was most common at points during the 1920s, 1930s and 1950s. So.. the graph doesn't obviously support your theory, I'd say. Hard to say. Perhaps Keats poetry sales are up since 1989?
Leaving out "John Keats" you can see much more detail in the remaining terms:
https://books.google.com/ngrams/graph?content=Dan+Simmons%2C...
This view seems to more clearly show Simmons having little effect.
Edit: I first tried ngrams using "Hyperion" but noticed many other things - software, books etc - had that title in the last few decades besides Keats poems or Simmons books. So I tried phrases that I thought would be more safely Keats-related only.