Dying doesn't automatically elevate people to legendary status. Pac and Biggie had several factors going in their favor before they died (some of it they didn't even ask for):
1) They were both dominant solo artists in Hip Hop at the time of their demise. No other rappers were as dominant during that '95-'97 period. There were only groups that were giving them competition. The Fugees, Bone Thugs N Harmony, and Wu Tang are the only Hip Hop artists arguably bigger.
2) Them having double LP's that felt like Greatest Hits and Best of projects didn't hurt either. AEOM and LAD were inescapable.
3) They had a solid foundation. While Biggie only had two albums, look at the massive amount of classics and hit songs on just those two albums.
4) The CONTROVERSY surrounding their deaths elevated them more than them dying. Add to the fact that death was a major theme in their music. It made it easy to create all these urban legends.
At the end of the day, it was the music that put Pac and Biggie at the status they are at.
Kendrick would still be where he is now. It's morbid to even think that someone has to die to be of status in Hip Hop.
Think about this: Nas and Jay are still alive and are considered by many to be GOAT. We even have people that consider Andre 3000 as GOAT and he doesn't even have a solo classic album. All that "if (insert random MC) dies today, he'd be Biggie and Pac status" talk needs to be deaded.