At the San Diego Comic Con 2014, there was what they call an hologram of Homer Simpson, but is this a real hologram? Or was it, perhaps, just a projection on the wall? I thought that the hologram technology was far from those kind of impressing results!? If it's really hologram technology, how does it work?
Calling this effect a "hologram" is common, but a misnomer: (http://www.hollywoodreporter.com/behind-screen/why-billboard-music-awards-michael-706269)
The imagery of Jackson -- and previously Tupac during his "performance" at Coachella in 2012 -- was actually created with an old magician's trick using a mirror, a 2D effect known as "Pepper's Ghost."
Since the Pepper's Ghost technique has been sufficient to produce this effect in the past, there is no reason to posit a technological leap for this instance.