My interpretation of the God Beyond was that it was basically left open on purpose so readers could project their own beliefs onto the books. E.g. If your an atheist you may choose to believe that the characters die permanently, and if you are religious you may choose to believe that the characters in the books go to an afterlife etc. Basically, just like there is no way to prove if there is a god or not in the real world, there is no way to prove it in the Cosmere and no character or being within the cosmere will ever truly know what happens in the Beyond. Thats what I took away from it anyway...
