I don't know about revenue, but I suspect multiple other labs are already beating OpenAI/Anthropic on profitability. Staying on the frontier is expensive, and it's hard to recoup those R&D costs when you have a bunch of other labs nipping at your heels.
If you concede the previous point, then the only way for OpenAI/Anthropic to keep growing long term is to swallow the whole economy (i.e. mass job replacemnt), and that's a bet I wouldn't take.
If they can carve out a niche of industrial and governmental partners who rely on them for sovereignty reasons, it may be enough.
The second moat is convenience, which all the big labs make it (comparatively) easy to glide into their models.