I guess it depends on what you mean with "finish". I am still positive that there will be the planned 10 SA books. And the same with the planned Mistborn books, even though it will be quite some time till we get to read them. But all in all, Brandon Sanderson is still young and if fate is willing, also has lots of time to get the stories done the way he wants to. Compared to fans of George R.R. Martin, we got it easy.
Also, I really don't mind the non-Cosmere books, since I enjoy those too. But I can understand that readers who don't feel that way might be annoyed with every new book that doesn't add to the Cosmere. Still it feels like unjustly complaining when it's pretty openly communicated that the book after is a Cosmere book again.