Excellent series and the one wrap up book running to three was fine with me, There were so many plot lines I thought one book would not do it justice. Brandon Saunderson is finishing off Robert Jordan's work and as Jordan knew he was dying he left lots of notes on what was meant to happen (and wrote the final scene himself before he passed).
The last book is due out early next year but read here to find out more
http://www.brandonsanderson.com/blog/1058