When Watchtower (and the other religious institutions) are overthrown with a swift pitch, that will be evidence.
No, there could be any number of reasons why religious organisations could become defunct. And offering some hypothetical future event as 'evidence' isn't particularly compelling.
Jesus said it would happen. So it will happen.
You don't have any evidence that Jesus said it would happen, let alone that he would be necessarily correct. According to the 'gospels', which were written decades after Jesus' death and can't be regarded as reliable sources for anything Jesus said anyway, Jesus said his 'presence' would be within a generation of his ministry. That failed, so he's not reliable from the outset.