Is your theory really that closed source software will just stop being developed? I can't find another way to read that, but you can't think Google is just going to give up and shut down, right?
But why invest time and money when your features get copied as soon as you publish it?
Because you still get money?
Nothing about getting copied means you don't still get money. It probably just means your legal team has some people to annoy into going away if you're a big company.
That may well be the future for most commercial software (and software engineers) as margins collapse and AI tokenomics moves more power from labor to capital.