An interesting idea if there's a sequel

Let's say down the line years later, in the event Alex Hirsch decided to go back to the world of Gravity Falls (he can't speak for future Alex after all) what kind of story would he do?

Dipper and Mabel's story are pretty much over, so he ain't regurgitating that (although I hope for some Dipcifica in the college years.)

But what I can imagine is something grander than even his own Gravity Falls. I can imagine what we've seen throughout the series and even the finale are just small snippets of a much, much BIGGER picture. I thought if he were to return one day, he would return the same way Tolkien returned to Middle-Earth years after The Hobbit: Tell a grand, mammoth story that would be one of the pillars of the medium. Gravity Falls would be his Hobbit, so naturally the sequel would be his Lord of the Rings.

I have no idea what that story would be, but I imagine Bill Cipher would be either be the Sméagol/Gollum or a Randall Flagg figure (Dark Tower) that is second in command to an even greater evil. What do you guys think?

There's definitely no arthritis in this group!