In an email from Sanderson (who has a very good reputation about communicating directly with his fans), the author confirmed that there are still plans for two more Mistborn trilogies. He suggests that the series will eventually be a ‘trilogy of trilogies.’ These do not include the “Wax and Wayne” books, though there are more of those coming, too. He says, “they’re not so much ‘prequel’ as they are a side venture into life between the first and second trilogies, but they will be used to provide some foreshadowing for the second trilogy.”
For the first time (I believe), Sanderson also described some early plot elements and setup for the next Mistborn trilogy:
As I envision it now, the second Mistborn trilogy, take place in a more technologically advanced version of the world, several hundred years later. They’ve progressed beyond steam technology to combustion engine technology, are building skyscrapers and that level of technology. It will follow the exploits of a team of Allomancers who are kind of like an Allomantic SWAT team, group of hybrid mercenary/deputized individuals who are brought in by the police to take out Allomancer criminals. The first book will deal with when they are called in to deal with a Mistborn serial killer. That’s how it starts. It will go bizarre from there, of course, but think guns, cars, skyscrapers, and Allomancers.
It’s amusing, and likely intentional, to see that Sanderson has swapped out the crooked band of criminals from the first Mistborn trilogy with a law enforcement-type group of mercenaries. Fans of Sanderson know that he’s halfway decent at writing enjoyable group chemistry, but the true selling point, in addition to his complex plotting, will be to see how he utilizes Allomancy in a semi-modern era. Readers had a taste of how Allomancy, a magic system that can manipulate metals, can affect and be affected by guns in The Alloy of Law, and it sounds like Sanderson plans to take this concept even further with the upcoming trilogies, as he advances the technology level in the world. in The Alloy of LawThe appearance of a mysterious character event at the end of The Alloy of Law is likely the first of these ‘foreshadowing’ moments that provide hints about the overall story arc of the upcoming trilogies.
There is no known release date for any of these novels.