This is a different take than your regular Green Lantern Corps series. So it may not be your kind of book. I wouldn't say that there's "zero" progress on the mystery. There's just lots of places for the Green Lantern Corps to explore and learn. And we should be able to learn more about Relic's universe from a different perspective later down the line.
I hope this is true. Cullen Bunn answered on some interesting questions on reddit. The ongoing series is desired to last around 14 issues. I don't know if that's considered a mini or not though. He says that he needs at least a year to tell the story.