Imo pac has already been surpassed. Time and time again. nikka was a fake, pseudo intellectual. wannabe profit. Period. And his songs honestly didn't go that hard. Plenty of rappers that i would put above pac.
I don't think they'll ever be another rapper as good as BIG. Imo that nikka was fake too. But the way he was able to mix the street lyrics with the commercial beats/production was fire. And if you listen to dudes first two albums they're basically hit, after hit, after hit, after hit. I can listen to both of those albums back to back and not skip a song or interlude. I've been bumping his shyt since 2001 and i'm still not tired of it. Still never hear a song and think "aww this shyts super corny why did i ever bump it". His work is timeless.