Will it be compatible in any way?
Or have we to wait for a revision of the Osmo RAW?

This has been discussed a few times here.  The X5S does NOT have the processing unit for the camera in the gimbal/lens mount element like the other cameras.  From what I understand in order for the camera to process 5k raw footage and to maintain sufficient speeds in terms of IO reading/writing to SSD, they had to put the processor in the bird.  Therefore if this is true, we need a brand new osmo that has a process in it.  I would assume DJI will make one (I hope, gulp) but I would expect it to cost more than what is currently available today for the regular X5.

One of the biggest problems on these forums is that "there is no easy way to filter out the rubbish when searching for an answer to a problem" so many questions being asked for the same answer.
No the osmo can't accept the X5S and the X4S but DJI is planning a new OSMO (Mount3)