I don't know how they are going to separate Spider-Man and Venom without drastically altering the character. I really don't know why they would anyway..seems to be a bad move imo.
My fear is that it's going to be Catwoman with Halle Berry or Steel with Shaq all over again. Both had potential to be great films, but the characters just didn't work once separated from their source characters of Batman and Superman. You can't just take a character that exists because of another and separate if from its universe and expect it to work. It won't.