You're much more confident than I am that the researchers at OpenAI (or anyone else currently alive) are masters of their craft to such an extent that they
would even be able to predict whether the next big training run they do will result in a superintelligence or not. Another way of saying the same thing is to say that the only way anyone knows that GPT-4 is not dangerously capable is that it has been deployed extensively enough by now that if it was going to harm us, it would've done so by now: not even the researchers that designed and coded-up GPT-4 or watched it during training could predict with any confidence how capable it would be. For example, everyone was quite surprised by its being able to score in the 90th decile on a bar exam.
Also, even if they never produce a superintelligence, they are likely to produce insights that would make it easier for other teams to produce a superintelligence. (Since employees are free to leave OpenAI and join some other team, there is no practical way to prevent the flow of insights out of OpenAI.)