I can see GPT-3 being used in a tool/add-on ala Intellisense or Tabnine, but as something to create "a way for anyone to ship a functional web app just by describing what it should do in natural language" (quoted from his website) I'm positive that we have to wait for at least a GPT version that doesn't get confused after ~200-300 words.

I guess you could create some kind of UI prototyping app, but better options for that already exist, which don't require you to write everything out.