Season 4 introduces many changes to the old system of kill and assist rewards.
While the Killstreak and Deathstreak tables are the same, the mechanics around the rewards are now different.
In order to reduce the effect of early-game wins (such as a level 1 teamfight), the gold bounty is being reduced to 60% at the beginning of the game. From 2 minutes to 4 minutes, the gold bounty scales linearly up to the full value.
Assists are also being reworked to benefit players who tend to get more assists than kills. In addition to their take of the assist pot, players with 2 more assists than kills gain 30 gold per assist. This increases to 45 gold for players with 3 more assists than kills, and 60 gold for players with more than 3 more assists than kills.
The amount of gold in the assist pot is changing as well. Until 20 minutes into the game, the assist pot is worth 50% of the kill bounty. This scales linearly up to 80% at 35 minutes into the game.
Finally, to counteract proxy farmers, players currently on a death spree will have their deathstreak reduced by 1 stage per 1000 gold earned from minions and monsters.