As always, the best answer to this will be contained in the State of the Sanderson newsletter that I write each December. You can sign up for the newsletter, or just look for it in my blog.
People ask me for prequels all the time. They’ve asked for MISTBORN prequels, ELANTRIS prequels, WARBREAKER prequels, etc. My general answer to this is probably not—just because I as a reader don’t like prequels. I’m one of those readers that if the ending is spoiled for me, in many ways that can ruin the book. Because of that it’s hard for me to decide to write a prequel.
Lots of my books are going to have sequels… one of these days. I have so many projects I could be working on that your particular favorite may not be on top of the list. Keep looking at the State of the Sanderson, and cross your fingers.