I'm not sure if this is what you're suggesting, but I can't imagine we will ever see someone producing entirely new Tupac songs based on his phoneme library.
It would be in such bad taste that even the American recording industry wouldn't go near it. People already get upset that they use old entire recordings to produce new songs, and those are actually his lyrics and his voice.
On a much smaller scale, this has already been done. Tupac's posthumous "Loyal to the Game" album produced by Eminem had a number of lyrical phrases constructed out of phonemes.
There was a small amount of outrage at the time of its release, but it mostly focused on the fact that those constructed lyrics were endorsing other rappers (mostly Eminem's protégés also performing on the track), whom some fans felt Tupac would not have endorsed had he been alive.
Definitely, but I think it is a question of scale.
It's one thing to construct some ad-libs, but to actually create a piece of art (i.e. an entire verse) is a whole different ball game. It would be like if someone took fragments of Picasso paintings, constructed an entirely new painting, and called it a Picasso.
I suppose it's conceivable that someone might try to do it, and it's apparently technically possible, but I think it would be roundly rejected.
To paraphrase the well-known maxim, you can never go broke underestimating the good taste of the american public (over a long enough timeframe). The IP status of the voice is a really fascinating question though, given how complex the current songwriting/master/recording breakdown is already.
It would be in such bad taste that even the American recording industry wouldn't go near it. People already get upset that they use old entire recordings to produce new songs, and those are actually his lyrics and his voice.