First you need to be clear about is that no one "believes" in the Big Bang. Is a scientific theory, and as such, is backed up with one thing you need to learn and is EVIDENCE. However, science always evolves and always looking for answers to questions. Questions that you don't ask, and just "believe" someone just popped-up the world into existence, because that's veracious, right?

Again, if new evidence comes to light thanks to technology improvements, and proves it's not the Big bang, then it will PROVE something else did. And science will change it based on the current evidence. Evidence that's challenged by other scientists and only 2 results can happen: or they replicate the result and cement that the new evidence is strong, or else new investigations will ensue to reach the truth. That's how science works. No beliefs. Just results and evidence.