I'm bullish on novel exploits too but I'm much less confident in the prediction. I don't think you can do two network pentests and not immediately reach the conclusion that the need for humans to do significant chunks of that work at all is essentially a failure of automation.

With more specificity: I would not be at all surprised if the "industry standard" netpen was 90%+ agent-mediated by the end of this year. But I also think that within the next 2-3 years, that will be true of web application testing as well, which is in a sense a limited (but important and widespread) instance of "novel vulnerability" discovery.