1. Biggie and 2Pac would have fallen off, eventually.
What goes up, must come down, but rappers killed in their prime are forever preserved in the amber of their most unimpeachable moment.
If Big and Pac had made it into the 2000s, they'd probably be recording house music with Nicki Minaj, dealing with drug addiction like DMX, recording acclaimed but ultimately underwhelming sequels to classic albums like Raekwon, or fighting off diminishing expectations like Nas.
All that said, we do wish both of them were still around. It would be cool to see Pac or Big meeting America's first black president, if only because Pac saw it as heaven-sent.