They already have a massive moat. Try competing with them, let me know what the bill looks like. Only a few companies on the planet can realistically attempt it at this point. Let me know how many GPUs you need and where you plan to get them from.
They have the same moat that Google search has. Including as it pertains to usage and data.
You also can't train a new competitor like OpenAI was able to jumpstart GPT, the gates have already been raised on some of the best data.
Very few companies will be able to afford to keep up with the hyper scale models that are in our future, due to the extreme cost involved. You won't be able to get enough high-end GPUs, you won't be able to get enough funding, and you won't have a global brand that end users recognize and or trust.
The moat expands as the requirements get ever larger to compete with them. Eventually the VC money dries up because nobody dares to risk vaporizing $5+ billion just to get in the ring with them. That happened in search (only Microsoft could afford to fund the red ink competition with Google), the exact same thing will happen here.
Google search produces $100+ billion in operating income per year. Venture capital to go after them all but dried up 15+ years ago. There have been very few serious attempts at it despite the profit, because of the cost vs risk (of failure) factor. A lot of people know how Google search works, there's a huge amount of VC money in the tech ecosystem, Google mints a huge amount of profit - and yet nobody will dare. The winner/s in GPT's field will enjoy the same benefit.
And no, the open source at home consumer models will not come even remotely close to keeping up. That'll be the latest Linux consumer desktop fantasy.
That would be a Nuke in the AI world.