At this time, there is no data cap.
I have read rumors of a future intent to institute a data cap, but they are unconfirmed internet ramblings at this point.
Maybe Elon knows, but he isn't telling. And maybe he doesn't know...
All things considered, that’s a pretty competitive price for a lot of markets, if the download speeds really are as advertised. Where I live, it wouldn’t be a good deal at all. But, we have a reasonable number of broadband service providers available to us. I’ve got some family that live in suburban OH and they pay an astronomical price (close to $200/mo)for only 100 Mbps.