Actually, he said in a 97 interview that a last set of books was always in the back of his mind. It's just taken him a while to get around to them. In the preface to one of his books, he talks about his writing cycle - novel(s), short stories, mysteries. I think that it just came time to write epic fantasy again, and those books that were churning in the back of his mind came forth.
Donaldson has to remain very focussed when he's writing. If he browsed through this site, he'd never get anything onto paper. Too many ideas, questions, etc. to process. I sometimes feel overwhelmed myself!
