I think the writer had a vague plan at the start, but nothing beyond that. This is pretty much proven out in books 5-10 where he rambled on and on about basically nothing. When called on it, he said he'd do better and he did on the next couple, but then fell ill.

He managed to write up his ending notes and hand his notes to Brandon Sanderson before he died. But I don't think those notes were written before that.