I've never maintained software long-term so i could be wrong, but I interpret "code is cheap" to mean that you can have coding agents refactor or rewrite the project from scratch around the design correction. I don't think 'code is cheap' ever should be interpreted to mean ship hacky code.

I think using agents to prototype code and design will be a big thing. Have the agent write out what you want, come back with what works and what doesn't, write a new spec, toss out the old code and and have a fresh agent start again. Spec-driven development is the new hotness, but we know that the best spec is code, have the agent write the spec in code, rewrite the spec in natural language, then iterate.