Honestly, I wouldn't be surprised if OpenAI has done the math and determined that even releasing frontier quality models wouldn't put much of a dent in either their B2B or B2C businesses. Or, rather, that any such dent would be vastly overshadowed by the value of fending off potential competitors.
I haven't looked too much into Deepseek's actual business, but at least Mistral seemed to be positioning themselves as a professional services shop to integrate their own open-weight models, compliant with EU regulations etc, at a huge premium. Any firm that has the SOA open model could do the same and cannibalize OpenAI's B2B business---perhaps even eventually pivoting into B2C---especially if regulations, downtime or security issues make firms more cloud-skeptical with respect to AI. As long as OpenAI can establish and hold the lead for best open-weight/on-premise model, it will be hard for anyone to justify premium pricing so as to generate sufficient cash flow from training their own models.
I can even imagine OpenAI eventually deciding that B2C is so much more valuable to them than B2B that it's worth completely sinking the latter market...