I think that if you come at this as purely a set up for The Legion, you’re going to be disappointed, because it’s really not. It’s part character study (just how crazy would a person go if she lived for a thousand years) and part future world-building.
This two-part series of snapshots is a component of Brian Michael Bendis’s HUGE plan for his corner of the DC Universe (okay, a bit bigger than a corner). From the very beginning, even while Man of Steel was coming out, he said he wanted to do a story that would knit all of the disparate futures of the DCU together - into something that he was calling The Unity Saga.
We’ve been seeing one end of that in the ongoing Superman book. We’ll see the other end of it in his LSH book.
THIS story is about everything in between, seen through Rose/Thorn’s eyes, cementing one central DC Timeline into place, almost like the classic History of the DC Universe did.
Take a look at the eras that Millennium solidifies:
-The near future
-Batman Beyond’s future
-Kamandi and the Great Disaster
So now everything in this book is canon. That’s the kind of thing a fan like me enjoys - I love these kinds of specifics. Heck, I still miss Who’s Who.
Anyway, I’ve digressed.
I enjoyed the first issue, I guess that’s what I’m saying.