Nope, it's not a settled question in the way that I think you mean. Each ToS is different so each would be subject to individual legal analysis in court on its own terms.

Questions would include whether the ToS is unconscionable, whether the terms violate laws of the locality/nation, and so forth.

It's the same with traditional contracts - the fact that contracts have been around for hundreds (maybe thousands) of years doesn't mean much if you and I create a brand new one between us. Our contract's specific terms (and events/actions between us as a result) would be the issue in court.

That's like saying "If the gun fires the bullet, who is liable for murder?" It's a silly question.