These copilots are based on languages like python and java. This knowledge can be collected from the internet, for example from stackoverflow. But for Mendix there is no processable language (only screenshots of microflows) and not much information in a specific format, so I won't expect it soon, unless Mendix itself is working hard on this subject.
Great Idea Zhang!
Chris is right in that it's easier to add a GPT plugins for languages like Java or C#.
The problem is that Mendix codes are not widespread and open online available.
However, I think it should be possible to add AI assists to Mendix and I think Mendix should definitely work on these features as well.
Visual development in Mendix should not be a problem for Machine Learning as its just another input type for those LLM's.
And the XML language through the Mendix SDK's can also be used to train AI models on.
I am looking forward to Mendix 10 for this.
It's a big feature and probably no single partner will take on the job of developing it.