But, if model development stalls, and everyone else is stalled as well, then what happens to turn the current wildly-unprofitable industry into something that "it makes sense to keep spending billions" on?
The new OpenAI browser integration would be an example. Mostly the same model, but with a whole new channel of potential customers and lock in.
This can go either way. For databases open source integration tools prevailed, the commercial activity left hosting those tools.
But enterprise software integration that might end up mostly proprietary.
Citation needed. This is completely untrue AFAIK. They've claimed that inference is profitable, but not that they are making a profit when training costs are included.