I think that won’t happen any time soon. You may think that it will never happen. But the Nazis happened. The Soviets happened. So, you never know what will happen in the future. And, it isn't what I think or even what you think that matters. It is what the people who choose to attack us think.
If China wanted to preemptively attack us based on our possession of WMDs they could justify it. They couldn’t last year, because we had an international law against such things. This year things are different. You could say that they wouldn't attack us, because we are the only superpower, and you would be right. However, you need to consider 30 years down the road when China becomes the new superpower, or the co-superpower. History isn't stagnant. In thirty years China may view us as a threat, especially if we have a string of right wing Fundamentalists presidents in the White House. Heck, even Europe will see us as a threat.