Brandon Sanderson and Tim Patrick Rothfuss started signing each other's books for awhile too. I read that Sanderson signs his and Rothfuss books at the airport bookstore when he's traveling. I managed to find a few signed Sanderson books at the airport bookstore in SLC when I flew through there for a connecting flight once. I still have them on my bookshelf. No cross-signings though.
Yes, I had to think about it for a minute before I even came up with "Tim Rothfuss". He used to be a household name, and then he just stopped writing. Idk what his deal is, but he did say once that he's envious of Sanderson's writing speed. I guess it takes him a long time to write a book, and it seems like he either got burned out, or ran out of ideas. I felt like he took some ideas from Jordan in the 2nd Kingkiller book. I met him once, walking around on the floor at Emerald City Comic Con. He seems like a cool guy. He spent like an hour talking to my sister at his booth after I ran into him. It's a shame that I think you're right. It doesn't look like he'll ever finish that trilogy.
Whoops! I just deleted my original reply because I thought I was replying to another conversation I'm having about Jordan and Terry Goodkind.
The author I'm referring to is Robert Jordan, author of the Wheel of Time series. The warrior culture that Kvoth goes to live & train with in the 2nd book seem to be almost a direct copy of Robert Jordan's Aeil from the Wheel of Time series. That said, Jordan inspired a lot of writers, including Brandon Sanderson. Sanderson was able to finish Jordan's epic 14 book story, when Jordan's health started failing and he reached out to Sanderson to take over the project. Sanderson wrote (I think) the last 2.5 books in the series.
Robert Jordan, author of the Wheel of Time series. The idea of females dominating male casters comes from Jordan, as do the crusader guys that chased down casters, those are Jordan's Whitecloaks (Children of the Light). There were a lot more ideas that seemed to have direct correlations, but I can't remember them now. The Whitecloaks were the most glaring copies though.