There would need to be significant capabilities that openai doesn't have or wouldn't be built on a short-ish timeline to have the enterprise switch. There's tons of bureaucratic work going on behind the scenes to approve a new vendor.
They make the point that there will be SaaS but it's likely to be more mom & pop SaaS and not significantly large players because the cost of producing software has been lowered significantly. The SaaS to emerge will live in their own specific niches.