as far as CGI I still want a short film/music video released using the unused motion detection from Ghosts.. It could come out even more realistic than the young Arnold on Terminator...
I'd have to disagree with you there. The CGI Young Arnold in Terminator Genisys is incredibly state of the art and the detail on his model is absolutely ridiculous (see link below). They based Young Arnold's movement on an actual stand in actor, and any unnatural movements on top of that would look 'natural' since The Terminator is a cyborg/robot.
Motion capture definitely helps but the VFX in Terminator Genisys would be extremely expensive (taking into consideration that the music video will probably not make them as much money as a new Terminator film would). Even then, the CGI model still utilised the help of Schwarzenegger, I believe I watched somewhere that he allowed them to capture his face so they could get accurate mouth movements and the like.
That last part creates a huge problem for us as, obviously, Michael isn't here. Assuming they have that data backed up somewhere, they might be able to base it off the moves in Ghosts, but close ups of his character would be very difficult. In addition, motion capture has come a long way since 1996 so it wouldn't be as detailed as motion capture today. In saying all of this however, the CGI we see for 'digital doubles' is actually improving at a very rapid rate. Compare the digital Schwarzenegger in 2009's Terminator Salvation to the one in the new Terminator and you'll see how far we have come (other examples include Tron Legacy (2010), the first Captain America (2011), compare that to the new Terminator and... Ant-Man I think it was).
So while it might be possible in a few years, to expect anything near the level of young Arnold from the MJ Estate just wouldn't be realistic. What you saw at the Billboard Awards last year is pretty close to what you could expect (and even that was full on), but I'd be relatively happy with that given the circumstances... just improve it's dance moves
Rather technical, yet fascinatingly in-depth article on the new Terminator if you're interested:
http://www.fxguide.com/featured/terminator-new-makes-new-models-new-vfx/ Same website has an article on the MJ 'hologram' too, just search his name on the site