We already have languages for expressing abstractions, they're called programming languages. Working software is always built interactively, with a combination of top-down and bottom-up reasoning and experimentation. The problem is not in starting with real code, the problem is in being unable to keep editing the draft.
On the other hand, I expect that programming languages will keep evolving, and the next generation or so might be designed with LLMs in mind.
For instance, there's a conversation in the Rust's lang forum on how to best extract API documentation for processing by an LLM. Will this help? No idea. But it's an interesting experiment nevertheless.
