Don't think it's a tribute, more an exploitation of his image for money purposes. Dr Dre is behind this and is planning to take him on tour. The funny thing is, Tupac didn't even like Dre, he regularly dissed him later on in his career.
Also, just for people wondering about the tech behind it. It isn't a real hologram apparently, but a screen, some kind of mirror technique. He's actually 2D.
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