I think you mean software engineering, not computer science. And no, I don’t think there is reason for software engineering (and certainly not for computer science) to be plateauing. Unless we let it plateau, which I don’t think we will. Also, writing code isn’t a solved problem, whatever that’s supposed to mean. Furthermore, since the patterns we use often aren’t orthogonal, it’s certainly not a linear combination.

I assume that new business scenarios will drive new workflows, which requires new work of software engineering. In the meantime, I assume that computer science will drive paradigm shift, which will drive truly different software engineering practice. If we don't have advances in algorithms, systems, and etc, I'd assume that people can slowly abstract away all the hard parts, enabling AI to do most of our jobs.