If AI companies in the US are penalized for this, then the effect on copyright holders will only be slowed until foriegn AI companies overtake them. In such cases the legal recourse will be much slower and significantly limited.
Access to copyrighted materials might make for slightly better-trained models the way that access to more powerful GPUs does. But I don't think it will accelerate foundational advances in the underlying technology. If anything, maybe having to compete under tight constraints means AI companies will have to innovate more, rather than merely push scale.