I only came across this the other week, but given a lot of guys here have read at least Mistborn and Elantris and probably Way of Kings, I thought it was odd I'd never seen it brought up before.
The Wertzone: Brandon Sanderson plans 36-volume fantasy series
tl;dr: All of Sanderson's books are part of a great universe / concept that will eventually consist of around 36 books. Also relevant, two more Mistborn trilogies are planned, beyond the Alloy of Law stuff. One to be set in modern era technology and one seems like a space opera almost.
Finishing book 36 gives me something to look forward to when I'm 50.
Funny, I read that just yesterday and wanted to post it.
If he can make this fit together as logical as he worked out all the details in the Mistborn trilogy, I am really looking forward for all of this! Seems like I need to start to read some of his other books.