Though Riot are calling it an update, Rengar's entire kit has basically gotten a buff, and what is that if not a rework? Let's just hope he doesn't get too OP.
As Riot state, the goals of this update were to smooth out Rengar's gameplay, keep his current playstyle, and clarify his builds.
They plan on keeping a close eye on the Q crit damage ratio so he doesn't get too out of line, while also knowing that Q no longer applying on plants can be painful for seasoned players who used this mechanic to optimize Ferocity stacks. The thing is, though, the fact that it no longer works on plants is the only nerf to Rengar in this update.
Now, Rengar has a Ferocity resource bar that indicates how much Ferocity he currently has, where stacks generated by leaps will have a different color so you'll know if you'll gain Ferocity on your next leap. Speaking of which, Rengar can now leap after 0.35 seconds in brush or camouflage consistently, compared to the previous 03-0.45 seconds timer.
Rengar's Q-empowered basic attack is now always a critical strike. Instead of regular critical strike damage, each 1% critical strike chance increases this empowered attack's damage by 0.66% percent, while his W, Bola Strike, can now be cast mid-leap, with an instant cast, which also gives him vision on the enemy hit and 150 units around said enemy, for 2 seconds.
And lastly, his ultimate now offers not only true sight but also normal vision of 100 units around the nearest enemy. With all these changes, you can now neither run nor hide from Rengar.