Most of the epilogue of Rainbows End really feels like a sequence at the end of a movie where we get a line or two about what happened to the characters: Bob and Alice are still in the military, Miri and Juan are becoming friendly again, Lena still isn't talking to Robert, and Robert is still enjoying his newfound talent for math/science.
And then it goes on some more: Winston Blount has a low-level job at the university, Carlos Rivera got cured of his JITT seizures, and the library is curiously split between the different belief circles.
We don't know what happens to Vaz, Braun, and Mitsuri, but we do hear that there are rumors of scandal (Epilogue.1). Unfortunately for us, those rumors don't turn into actual news.
In fact, most of the epilogue seems devoted to how the library is doing, which is that (a) it's still standing but (b) there are a lot of changes going on—and some of them are interesting to Robert.
Our interpretation of the title (check out our analysis in action over at "What's Up With the Title?") goes into this more, but the epilogue seems to say that, when something ends, something else begins. Which sounds like the sort of happy-dippy thing a motivational poster says. But we can't deny the fact that Robert once fought very hard to save the physical books and now he thinks the virtual books are really cool.
Also, at the epilogue, Carlos and Robert discuss whether Rabbit might still be alive somewhere and might still fulfill his promises. Which means that Robert might be able to have it all: the poetry, the math, and the not-being-a-total-jerk. So: some rainbows end—and maybe other rainbows start.
Also, does Robert's last line—"What if I can have it all?" (Epilogue.68)—sound like sequel bait to anyone else?