The P4 and P3 .DAT files are similar. They both get recorded onto an internal SD card that is very difficult to access physically. They are both encoded which allows the internal bus to be more efficient. In the case of the P3 the .DAT can be directly accessed via the USB port. All it takes is a file copy.
If we were able to access the P4 .DAT in the same way; i.e., just a file copy then it should be relatively simple to determine the format and DatCon would work for P4 .DAT files.
@FredzMaxxUAV obtained a set of these P4 .DAT files when he had the P4 disassembled and was able to physically extract the SD card. I was then able to use some of the tools that I developed to reverse engineer the P3 .DAT file. The P3 and P4 .DATs use the same kind of format but are different enough that it would require some work to to determine the format.
The real problem is that, so far, we've been unable to get a copy of the internal SD card's .DAT file. Unlike the P3, there is no way to directly view and retrieve the internal .DAT files on the P4. Instead the P4 .DAT files are retrieved via the DJI Assistant app which then produces three files that can be sent to DJI. I've looked at these files and they are either encoded, compressed or encrypted. It doesn't make much sense to encode them. There isn't much to be gained by compressing the internal .DAT file since it already has a lot of entropy, i.e. it can't be compressed much further. But, I did look at the obvious compression schemes.
I think the files that the DJI Assistant produces are probably an encryption of the internal .DAT file. If so, then it's effectively impossible to retrieve the internal .DAT file from these files.
One possibility is to determine how the DJI Assistant produces the three file from the internal .DAT. If the bits coming across the USB to the DJI Assistant aren't encrypted then it should be possible to mimic the DJI Assistant and get those unencrypted bits.
@Hans 75 attempted to use a USB sniffer but didn't get very far.