I've sort of written a sequel to my epic WIP. A friend of mine liked the world, and we did an rp set after the end of the (still) unfinished story. It's decidedly AU because it doesn't take into account developments in the most recent six chapters or so, but there are elements of it that I'd probably use if I were to write a sequel to the story after it's actually finished.

I do have a set of stories that are in an arc. I started with one story and didn't intend to write more, but more came to me. I've also got a couple of fragments of sequels to other stories. They may never go anywhere. They've been stalled out for years. Who knows?