Open source will be bigger than ever, but not necessarily for the right reasons.
IMHO, as coding agents mature, we will see a surge in open-source projects. Most will remain obscure due to poor discoverability and growing competition for users' attention. But the same forces driving that growth in volume will likely erode quality and it most certainly raising ethical concerns. A company can now perform a clean-room reimplementation of an open-source project and potentially maintain it going forward with more resources and polish than the original.
For the most successful, high-impact projects, this creates a real problem that they risk losing momentum to well-funded clones.
At that point, what is the incentive to keep building in the open?